(19)
(11)EP 2 618 388 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
02.10.2019 Bulletin 2019/40

(21)Application number: 12151946.6

(22)Date of filing:  20.01.2012
(51)Int. Cl.: 
H01L 33/08  (2010.01)
H01L 33/00  (2010.01)
H01L 33/32  (2010.01)
H01L 33/18  (2010.01)

(54)

Light-emitting diode chip

Lichtemissionsdiodenchip

Puce à diode électroluminescente


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
24.07.2013 Bulletin 2013/30

(73)Proprietors:
  • OSRAM Opto Semiconductors GmbH
    93055 Regensburg (DE)
  • Universidad Politécnica de Madrid
    28040 Madrid (ES)

(72)Inventors:
  • Straßburg, Martin
    93093 Donaustauf (DE)
  • Calleja-Pardo, Enrique
    Alcobendas, 28109 Madrid (ES)
  • Albert, Steven
    28047 Madrid (ES)
  • Bengoechea Encabo, Ana Maria
    28020 Madrid (ES)
  • Sanchez-Garcia, Miguel Angel
    28001 Madrid (ES)
  • Mandl, Martin
    93138 Lappersdorf (DE)
  • Kölper, Christopher
    93049 Regensburg (DE)

(74)Representative: Epping - Hermann - Fischer 
Patentanwaltsgesellschaft mbH Schloßschmidstraße 5
80639 München
80639 München (DE)


(56)References cited: : 
EP-A2- 2 413 385
FR-A1- 2 904 730
US-A1- 2007 194 330
US-A1- 2011 240 955
WO-A1-2012/106814
US-A1- 2005 194 598
US-A1- 2010 148 146
  
  • LIN HON-WAY ET AL: "InGaN/GaN nanorod array white light-emitting diode", APPLIED PHYSICS LETTERS, AIP, AMERICAN INSTITUTE OF PHYSICS, MELVILLE, NY, US, vol. 97, no. 7, 16 August 2010 (2010-08-16), pages 73101-1-73101-3, XP012138836, ISSN: 0003-6951, DOI: 10.1063/1.3478515
  • CHANG Y-L ET AL: "High efficiency green, yellow, and amber emission from InGaN/GaN dot-in-a-wire heterostructures on Si(111)", APPLIED PHYSICS LETTERS, A I P PUBLISHING LLC, US, vol. 96, no. 1, 6 January 2010 (2010-01-06), pages 13106-13106, XP012130269, ISSN: 0003-6951, DOI: 10.1063/1.3284660
  • MI Z ET AL: "High performance InGaN/GaN dot-in-a-wire light emitting diodes on Si(111)", WINTER TOPICALS (WTM), 2011 IEEE, IEEE, 10 January 2011 (2011-01-10), pages 47-48, XP031930296, DOI: 10.1109/PHOTWTM.2011.5730039 ISBN: 978-1-4244-8428-7
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description


[0001] The document "On the mechanisms of spontaneous growth of III-nitride nanocolumns by plasma-assisted molecular beam epitaxy", Journal of Crystal Growth 310, 2008, pp 4035-4045, discloses a method for the production of III-nitride nanocolumns.

[0002] The document "N-face GaN nanorods: Continuous-flux MOVPE growth and morphological Properties", Journal of Crystal Growth, 315, 2011, pp 164-167, discloses a method for the production of N-face GaN nanorods.

[0003] The document "Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells", Nanotechnology 21 (2010) 305201 (5 pp), discloses a method for the production of N-face GaN nanorods.

[0004] The document EP 2 413 385 A2 discloses a III-nitride light-emitting diode and a method for producing the same. This document, published on 01.02.2012, claims the priority date of 29.07.2010. Its content as filed is therefore considered to be comprised in the state of the art relevant to the question of novelty only, pursuant to Article 54(3) EPC.

[0005] The document H.-W. Lin et al., "InGaN/GaN nanorod array white light-emitting diode", APPLIED PHYSICS LETTERS, vol. 97, no. 7, August 16, 2010, pages 73101-1 to 73101-3, XP012138836, ISSN: 0003-6951, DOI: 10.1063/1.3478515, refers to a InGaN/GaN nanorod array.

[0006] The document FR 2 904 730 A1 is drawn to a production method for electroluminescent nitride semiconductor devices.

[0007] The document WO 2012/106814 A1 is drawn to high efficiency broadband semiconductor nanowire devices. This document, published on 16.08.2012, claims the priority date of 11.02.2011. Its content as filed is considered to be comprised in the state of art relevant to the question of novelty only, pursuant to Article 54(3) EPC.

[0008] The document Y.-L. Chang et al., "High efficiency green, yellow, and amber emission from InGaN/GaN dot-in-a-wire heterostructures on Si(111)", APPLIEO PHYSICS LETTERS, vol. 96, no. 1, January 6, 2010, pages 13106 to 13106, XP012130269, ISSN: 0003-6951, DOI: 10.1063/1.3284660, is drawn to InGaN/GaN dot-in-a-wire heterostructures.

[0009] The document Z. Mi et al., "High performance InGaN/GaN dot-in-a-wire light emitting diodes on Si(111)", WINTER TOPICALS (WTM), 2011, IEEE, January 10, 2011, pages 47 to 48, XP031930296, DOI: 10.1109/PHOTWTM.2011.5730039, ISBN: 978-1-4244-8428-7, refers to InGaN/GaN dot-in-a-wire light emitting diodes.

[0010] It is one object to specify a light-emitting diode chip which has an emission of electromagnetic radiation which shows a particularly good thermal stability.

[0011] The invention is defined in claim 1. Embodiments of the invention are set out in the dependent claims.

[0012] According to the invention, the light-emitting diode chip comprises a semiconductor body having a plurality of active regions. For example most or all active regions are configured to emit electromagnetic radiation during operation of the light-emitting diode chip. It is possible that all active regions of the semiconductor body are configured in the same manner and emit electromagnetic radiation of the same optical spectrum within the fabrication tolerance of the light-emitting diode. Then again, it is also possible that at least some of the active regions differ from each other with respect to their construction and/or the optical spectrum of the electromagnetic radiation emitted during operation of the light-emitting diode chip.

[0013] For example the semiconductor body has a large number of active regions of at least one thousand active regions, in particular of at least one million active regions.

[0014] At least one of the active regions, in particular most of the active regions, for example all of the active regions, have at least two adjacent subregions. Both of these subregions emit electromagnetic radiation during operation of the light-emitting diode chip. The subregions of an active region are located spaced from each other within the active region. Each subregion consists of one quantum well structure. By employing such structures, the wavelengths of the light emitted by each subregion can be set particularly accurately.

[0015] The active region has at least one barrier region which is arranged between two adjacent subregions of said at least two subregions. That means that two adjacent subregions of an active region are spaced from each other by a barrier region which, for example, has an interface with both adjacent subregions. The barrier region can be arranged directly between the two adjacent subregions. The barrier region differs from the subregions which adjoin the barrier region by the composition of the semiconductor material forming the barrier region and the adjoining subregions.

[0016] For example at least one of the active regions, in particular most of the active regions or all of the active regions, has three or more subregions, wherein a barrier region is arranged between each pair of adjacent subregions of the active region.

[0017] The at least two subregions emit light of mutually different color during operation of the light-emitting diode chip. Thereby the subregions can emit light from the wavelength spectrum of UV-radiation to the wavelength spectrum of IRradiation. At least two of the subregions, for example two adjacent subregions, emit light of mutually different color. Thereby it is possible that for example one of the subregions emits blue light and the other subregion emits green, yellow or red light. It is further possible that at least one of the subregions emits mixed light which has no pure color. In this case at least two subregions of the active region can emit different mixed light of different composition. For example one of the subregions emits bluish-green light wherein another subregion emits greenish-yellow light during operation of the light-emitting diode chip. For example a further subregion emits red-amber light during operation of the light-emitting diode chip. In sum white light can be produced.

[0018] In at least one of the subregions the emission of light is generated electrically. In other words, the subregion of the active region is pumped electrically and the emission of light is not due to an optically pumping of said subregion. Thereby it is possible that each subregion of the active region is electrically pumped so that the emission of light is generated electrically in each subregion of the active region. Further it is possible that the active region comprises electrically and optically pumped subregions. For example, the active region comprises exactly one subregion in which the emission of light is generated electrically and one or more subregions which are optically pumped by the light emitted in said exactly one electrically pumped subregion. The barrier region between two adjacent subregions is configured to hinder a thermally activated redistribution of charge carriers between said two adjacent subregions. Therefore, the barrier region, for example, has a larger band gap than the semiconductor material of the subregion adjoining the barrier region. The fact that the barrier region is configured to "hinder" a thermally activated redistribution of charge carriers means that without the barrier region the thermally activated redistribution is more likely than with the barrier region. In other words, the barrier region reduces the probability of a thermally activated redistribution of charge carriers between the two subregions adjoining the barrier region.

[0019] In least one of the subregions the emission of light is generated electrically.

[0020] White light emitting light-emitting diodes can suffer from strong temperature dependency of the color temperature and of the color coordinates of the emitted white light. Above this, a significant efficiency reduction is observed with increasing temperatures for both white light generation with phosphor conversion or with light-emitting diodes of different color, where especially red light-emitting diodes are made of temperature-sensitive group III phosphides. In addition, the so-called "droop" in for example InGaN-based light-emitting diodes impairs high current operation due to sublinear increase of radiative emission and due to increased non-radiative losses like phonon-assisted Auger recombination and/or thermal escape and/or carrier overflow.

[0021] Today there is no real solution for these problems, but only some approaches mitigate these problems. For example regarding the "droop" effect, the light-emitting diodes can be operated at relatively low operation currents or at elevated currents with reduced efficiencies. With regard to the change of color coordinates depending on the operation temperature of light-emitting diodes phosphor conversion for temperature stable white color coordinates can be used by taking the burden of reduced conversion efficiency with increasing temperatures or relatively expensive solutions with light-emitting chips of different color. However, these solutions still suffer from a decrease in efficiency with increasing temperature. In addition, different materials for different colors would lead to different lifetimes of individual chips in solutions where light-emitting diode chips of different colors of emission are used. This limits the performance and the lifetime of such constructed light-emitting diodes.

[0022] For a here-described light-emitting diode chip the thermally activated redistribution of carriers is suppressed by the at least one barrier region. Hence, the ratio of photons generated in each subregion remains independent of the operation temperature and of the current density of the current running through the active region. Consequently, in the case of emission of white light by an active region of the semiconductor body the white light coordinates can be maintained nearly constant. In addition, each active region can be chosen to be thick enough to suppress the droop problem by providing a large defect-free volume for the light generation. In particular if the active regions are constructed as nanostructures like, for example, nanorods, an extraordinary high crystal quality can be achieved which allows for low non-radiative losses in the semiconductor material of the active regions.

[0023] These active regions have a direction of main extension. Consequently, the active regions are elongated structures and, for example, not in the shape of an, e.g., planar layer. For example each active region has a preferred orientation in the direction of main extension. For example at least one, in particular most of or all active regions have the shape of a cylinder, a cone or a prism for example with a hexagonal base area. At least some or all of the active regions are spaced apart from each other in a direction which runs in lateral direction with respect to the direction of main extension. For example most of or all active regions are arranged in a common plane which runs lateral or even perpendicular to the direction of main extension of the active regions. Further it is possible that at least some or all of the active regions partly touch each other in the lateral direction. In other words, side faces of adjacent active regions can be - at least in places - in direct contact with each other.

[0024] The subregions of an active region are arranged along the direction of main extension of their active region and at least one barrier region is arranged between each pair of adjacent subregions. Consequently, the active region is given by a sequence of alternating subregions and barrier regions. For example, if the active region is in the form of a cylinder or a prism, the subregions and the barrier regions can be given by sections of said cylinder or said prism which are stacked on each other in the direction of main extension of the active region.

[0025] The active regions are nanostructures and at least one of the active regions, in particular most of or all active regions of the light-emitting diode have a maximum diameter of 1000 nm and an aspect ratio of at least 3. A nanostructure is a nanoscale object having a diameter on its base which ranges from 1 to 1000 nm, for example 25 to 500 nm, in particular from 75 to 300 nm, preferably from 100 nm to 175 nm. The term "diameter" does not necessarily imply that the base of the nanostructure has a round shape. The maximum diameter denotes the maximum extension of the nanostructure in a direction perpendicular to its direction of main extension. For example the active regions are so-called "nanorods" which can be produced with an extraordinarily high crystal quality.

[0026] Further, it is possible that the nanostructure is, for example, a nano-column and/or a nano-pyramid and/or a mixture of both. The nanostructures have an aspect ratio (length divided by diameter) of at least 3. For example, the nanostructures can be directly produced on the top of a semiconductor body, for example by using a mask layer where the mask openings define the locations of the nanostructures. Further, it is possible that the nanostructures are produced independently from a carrier material and transferred to said carrier. Further, the nanostructures can be produced by etching into a semiconductor body.

[0027] Each subregion is based on a nitride compound semiconductor material.

[0028] In the present context, "based on a nitride compound semiconductor material" means that a subregion or at least one part thereof, comprises or consists of a nitride compound semiconductor material, InnGa1-nN or else AlnGamIn1-n-mN, where 0 ≤ n < 1, 0 ≤ m ≤ 1 and n+m < 1. In this case, this material does not necessarily need to have a mathematically exact composition according to the above formula. Rather, it can comprise, for example, one or more dopants and additional constituents. For the sake of simplicity, however, the above formula only comprises the essential constituents of the crystal lattice (Al, Ga, In, N), even if these can be replaced and/or supplemented in part by small amounts of further substances. However, a nitride compound semiconductor material always comprises nitrogen or a nitrogen compound.

[0029] Each subregion is based on a nitride compound semiconductor material comprising indium. Such an indium comprising nitride compound semiconductor material is a material that has a good thermal stability at the desired wavelength emitted or re-emitted by this material. However, high indium concentrations are difficult to achieve in conventional thin film structures, especially in thicker films (for example, having a thickness greater than 20 nm). However, it has been found that the indium content in active regions which are embodied as nanostructures can be very high without introducing crystal defects in the light-emitting structure, i.e. the semiconductor body.

[0030] In particular it is possible that each subregion comprises indium, in particular is based on an InGaN semiconductor material.

[0031] Each barrier region is at least partly based on a nitride compound semiconductor material having a greater band gap than the subregions adjoining the barrier region. The barrier itself can consist of a semiconductor layer stack with different compositions and therefore band gaps of which some can be in the range or even lower than the subregion band gap.

[0032] For example, if the subregions are formed with a material based on an InGaN semiconductor material the barrier region can be based on GaN or AlInGaN or InGaN with less Indium than the adjoining subregion.

[0033] The barrier regions are thinner than the subregions adjoining them. For example, the subregions have a thickness of at least 20 nm, in particular of at least 100 nm in the direction of main extension of their active region, wherein the barrier regions have a thickness of smaller than 1000 nm, in particular smaller than 100 nm, in the direction of main extension.

[0034] According to one aspect of the light-emitting diode, in at least two subregions of the same active region the emission of light is generated electrically. For example in this case all subregions of the active region are pumped electrically.

[0035] In this case the light in each subsection is predominantly generated by carrier injection.

[0036] In this case, a tunnel junction can be arranged between two electrically driven subregions. Thereby it is possible that the barrier region itself functions as a tunnel junction between two electrically driven subregions. For example, the electric contacts of the active regions are at the top and at the bottom of the plurality of active regions. Photons are generated by carrier injections in the active regions.

[0037] The tunnel junction can, for example, consist of two layers: A first layer is a p+ doped layer, e.g., p+ InGaN with an Indium content of >= 5%. A second layer is an n+ layer, e.g., n+ InGaN with an Indium content >= 3%.
A spacer can be arranged between the first and second layer and is introduced to prevent compensation of carriers. The spacer can consist of (Al,In,Ga)N. Spacer and/or both layers may consist of short period superlattices.

[0038] In particular, the band gap engineering of the active layer (internal or external electrical fields, gradient indium or discreet indium concentration in each subsection) allows specifically adjusted AlInGaN barriers with optimum barrier height and thickness to avoid carrier overflow and to provide required optical and electrical transparency of the barrier regions.

[0039] According to one aspect the barrier consists of AlInGaN of a composition with a band gap larger than the surrounding subregions, in particular of InGaN with a band gap larger than the surrounding subregions. The thickness of the barrier layer is smaller than 100 nm, in particular smaller than 20 nm, especially smaller than 5 nm.

[0040] According to one aspect of the light-emitting diode in at least one first subregion of at least one active region the emission of light is generated electrically and in at least one second subregion of the same active region the emission of light is due to optically pumping by light of the first subregion. For example the barrier regions are n-doped in order to localize a pn-junction in a blue light-emitting or UV-radiation-emitting subsection of the active region. In this subregion the light is generated electrically and used to optically pump the subsequent subregion which, for example, follows in the direction of main extension. For example in the following subregions optically pumped green, yellow, amber and/or red light is produced. Thereby, the active region can form a light guide which guides the light of the at least one first subregion along the direction of main extension to the at least one second subregion. In other words, the pump light is guided along the longitudinal axis of the active region which reduced the loss of pump light.

[0041] Advantageously the color coordinates and the color temperature of the light emitted by an active region can be adjusted by the number and/or the total volume of the subregions. For example by adjusting the indium concentration in each subregion, the colour of light produced in each subregion can be set. The indium content in each subregion can be determined via parameters like the growth temperature during fabrication of the active region, material fluxes and/or the growth rate during the growth of the subregions. The volume of each subregion can be varied by, for example, the distance of the barrier regions adjoining the subregion to obtain desired spectral distribution of the light emitted by the active region.

[0042] According to at least one aspect of the light-emitting diode chip at least one of the active regions is configured to emit white light. For example, the white light is mixed light which is composed by the light produced in the subregions of the active region. For example the active region comprises a subregion which emits blue light, a subregion which emits red light and a subregion which emits green light during operation of the light-emitting diode chip.

[0043] In the following, the here-described light-emitting diode chip is explained in more detail with regard to embodiments of the light-emitting diode chip.
Figure 1
shows schematic view of an embodiment of a here-described light-emitting diode chip.


[0044] In connection with Figures 2A, 2B, 2C, 3A, 3B, 4, 5, 6 the active regions for embodiments of here-described light-emitting diode chips are explained in more detail.

[0045] In connection with Figures 4 and 5, modifications which are not configured in accordance with the present invention are shown.

[0046] In the exemplary embodiments and the figures, similar or similarily acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better understanding.

[0047] Figure 1 shows a schematic view of a here-described light-emitting diode chip. The light-emitting diode chip comprises a semiconductor body 1. The semiconductor body 1 has a first contact layer 4. For example the first contact layer 4 is formed by a semiconductor material which is based on a nitride compound semiconductor material. On one surface of the first contact layer 4 a plurality of active regions 2 is arranged. The active regions 2 are nanostructures which have a direction of main extension R and are spaced apart from each other in the lateral direction L which can be as small as that the nanostructures touch each other. For example, the active regions 2 are grown epitaxially on the top surface of the first contact layer 4.

[0048] Further it is possible that the growth substrate is removed and layer 4 is given by a carrier and/or a mirror layer. For example the mirror layer is formed with an Ag containing alloy having e.g. an Ag content <=100%. In this case the light-emitting diode chip can be of the thin-film design.

[0049] For example the active regions 2 are nanostructures which are epitaxially grown on the top surface of a semiconductor body. For example, the nanostructures are grown by means of MOVPE (metall organic vapor phase epitaxy) growth. Further, it is possible to grow the nanostructures by MBE (molecular beam epitaxy) growth.

[0050] The growth of the nanostructures can be performed in a self-organized way. Further is possible to use a mask layer for the growth of the nanostructures. For example a mask layer consisting of SiINx, SiO2, Ti and/or Ni is formed on the top surface of the semiconductor body. In this case, seeds for each nanostructure can be formed in openings of the mask layer directly on the top surface. The nanostructures then grow in the region of each seed. The use of a mask layer enables the formation of nanostructures at preselectable positions. This allows for an accurate setting of the density of the nanostructures. For example, the density of the nanostructures can be efficiently controlled by the number and position of openings in the mask layer which can be patterned e.g. by lithography or nano-imprint lithography which transfer the pattern into an additional resist layer and via a subsequent etching step into the mask layer and/or the extension of the openings of the mask layer. The use of a mask layer allows for the production of regular ordered nanostructures and e.g. position controlled nanorod growth.

[0051] Further it is possible that the nanostructures are grown by means of MBE growth and the semiconductor body is grown by means of MOVPE growth. In particular, the nanostructures are then grown by self-organized MBE growth. This yields structures with high aspect ratios and small diameters with, for example, a mean diameter for all nanostructures less or equal 70 nm, for example less or equal 50 nm. Consequently, a high density of the nanostructures can be reached by employing MBE growth of nanostructures. Further, the MBE growth of nanostructures provides excellent control of the indium concentration in the group III-nitride and indium concentrations up to 100% are possible. Therefore, MBE growth of nanostructures can be employed when especially high indium concentrations are needed.

[0052] In the embodiment of Figure 1 each active region 2 is shown as a so-called nanorod which has a cylindrical shape. Each active region 2 comprises subregions 21, 22, 23, 24 which are also of cylindrical shape, wherein barrier regions 3 are arranged between adjacent subregions. Thereby it should be noted that the subregions 21, 22, 23, 24 and the barrier regions 3 can exhibit any shape. There is no need for an identical shape of neighbouring subregions and barriers. Nevertheless, for the sake of simplicity all figures contain areas with disk-like or cylindrical shape.

[0053] The active regions 2 have a maximum diameter d of <1000 nm and a length 1 of at least three times the maximum diameter. Each active region 2 comprises subregions in which light of mutually different colour is produced. The area region 3 between the subregions 21, 22, 23, 24 hinder a thermally activated redistribution of charge carriers between two adjacent subregions. For example all subregions of each active layer can be driven electrically. In this case tunnel junctions 6 are arranged between adjacent subregions. Due to the junctions 6 each subregion emits light which is generated by carrier injection in the respective subregion. This allows a determination of the number of photons per colour, defined by the subregions, their indium content and their volume and the external quantum efficiency of each subregion.

[0054] On the other hand it is possible that only the subregion 21 nearest to one of the contact layers e.g. the first contact layer 4 is electrically driven and the production of radiation in the subsequent subregions 22, 23, 24 is due to an optically pumping of these subregions with light from the first subregion 21. As the highest efficiency of, for example, InGaN-based subregions is achieved in the blue spectral range, this is a very efficient solution. Due to the geometry of the active regions 2, the pump light generated in the first subregion 21 is guided along the direction of main extension R and thicker areas for efficient conversion of blue light to light of different colors are enabled. Thereby a good light coupling is achieved and all colors to be converted can be generated in InGaN-based material which additionally reduces interface losses between the subregions of different colour as there is a good match of the refractive index between adjacent subregions. In this case, it is more efficient to place the subregion emitting the longest wavelength, e.g. red, closest to the electrically driven pump region and the subregion of the shortest wavelength, e.g. green, furthest away in order to minimize reabsorption losses in longer wavelength subregions.

[0055] The light-emitting diode chip according to Figure 1 further comprises a second contact 5. For example the second contact 5 can be a layer which, for example, can be formed with a material transparent or translucent for the light generated in the subregions. For example the second contact 5 is made of transparent conductive oxide like ITO or ZnO. Further it is possible that the second contact 5 is a thin layer of conducting grapheme. But also other configurations of the contact 5 are possible.

[0056] Figure 2A shows a single active region 2 with three subregions 21, 22, 23. For example the first subregion 21 is configured to emit blue light, the second subregion 22 is configured to emit green light and the third subregion 23 is configured to emit red light during operation of the light-emitting diode chip. Figure 2B shows a similar active region 2, where barrier regions 3 having a greater band gap than the surrounding semiconductor material of the subregions are arranged between two adjacent subregions. Each active region has a first region 20 which is, for example, of the same material as the barrier regions 3. For example the first region 20 is based on GaN and n-doped. In this case the first region 20 e.g. consists of n-GaN. For example the subregions 21, 22, 23 are based on an InGaN-semiconductor material, wherein the barrier regions 3 are based on GaN or AlInGaN or InGaN.

[0057] Each active region can have a last region 30 (not shown in each figure) which is, for example, based on GaN and p-doped. The last region 30 is arranged on a side of the active region facing away from the first regions 20.

[0058] Figure 2C shows a comparison between the photoluminescence spectra for the active region 2 of Figure 2A without a barrier and the active region 2 of Figure 2B with a barrier. From the comparison it becomes clear that light produced by the active layer with barrier region 3 is brighter and the spectrum is broader than for active regions without barrier region 3.

[0059] In Figure 3A an active region 2 is shown having three GaN barrier regions 3 within an active region having a length of about 500 nm. The active region 2 has four subregions 21, 22, 23, 24, each having different but discreet indium concentrations to provide emission of blue, green, yellow and red light. Thereby the volume for the subregion 24 can be greater than the volume for the subregion 23, the volume of the subregion 23 can be greater than the volume of the subregion 22 and the volume of the subregion 22 can be greater than the volume of the subregion 21. Taking into account for the respecting quantum efficiency the volume of the individual subregions can be used to adjust the fraction of the corresponding wavelength in the total spectrum. Thereby, the size of the volume of each subregion compensates the different amount of pump light reaching the subregion and the different quantum efficiencies for the production of light of different colors in the InGaN-based material of the subregions.

[0060] Figure 3B shows a similar active region 2 with even more subregions in order to set a specific colour coordinate and colour temperature of the emitted mixed light. For example, the active region comprises two subregions 21, 22 for the production of blue light, two subregions 23, 24 for the production of green light, one subregion 25 for the yellow light and three subregions 26, 27, 28 for the production of red light.

[0061] Figure 4 shows an exemplary modification not according to the present invention comprising an active region 2 having four subregions 21, 22, 23, 24, each subregion emitting mixed light. For example the first subregion 21 emits greenish-blue light, the second subregion 22 emits yellow-greenish light, the third subregion 23 emits orange light and the fourth subregion 24 emits red light. For example, the different colors are produced by a gradient of the indium concentration wherein each subsection has an indium gradient where the previous subsection ends with the same indium concentration as the following section starts with.

[0062] Figure 5 shows an exemplary modification not according to the present invention comprising an active region 2 having two barrier regions 3, within an active region 2 having a length 1 of for example 800 nm, wherein each subregion 21, 22, 23 has a gradient indium concentration in the direction of main extension R. For example, each subregion is configured to emit white light and the barriers are tunnel junctions.

[0063] Thereby, it is possible that a here-described light-emitting diode chip has a plurality of active regions 2 which are all configured in the same way. Further, it is possible that one light-emitting diode chip comprises active regions of different composition such that at least two of the active regions differ from each other with respect to their composition.

[0064] In connection with figure 6 further examples for a here described active region 2 are given. For example the active region 2 can have the following configurations:

Configuration A.
20: n-GaN first region
21: electrically pumped blue light emitting InGaN subregion 31: p-GaN first barrier region which forms the electrical p-contact of the active region
22: optically pumped red light emitting InGaN subregion 32: second barrier region
23: optically pumped yellow light emitting InGaN subregion
33: third barrier region
24: optically pumped green light emitting InGaN subregion
30: GaN last region
In configuration A the current only runs through the electrically pumped blue light emitting InGaN subregion 21.
The first barrier region 31 is p-doped and forms a p-contact of the active region.

Configuration B.
20: n-GaN first region
24: electrically pumped blue light emitting InGaN subregion
31: n-doped first barrier region
23: optically pumped red light emitting (n)-InGaN subregion
32: n-doped second barrier region
22: optically pumped yellow light emitting (n)-InGaN subregion
33: n-doped third barrier region
21: optically pumped green light emitting (n)-InGaN subregion
30: p-GaN last region
In configuration B the current runs through all subregions. However, only the blue light emitting InGaN subregion 24 is electrically pumped.

Configuration C.
20: n-GaN first region
21: blue light emitting InGaN subregion
31: GaN or InGaN barrier region with gap energy of at least 3,4 eV
22: green light emitting InGaN subregion
32: InGaN barrier region with gap energy of at least 2,8 eV
23: yellow light emitting InGaN subregion
33: InGaN barrier region with gap energy of at least 2,4 eV
24: red light emitting InGaN subregion
30: p-GaN last region
In configuration C the current runs through all subregions. However, only the blue light emitting InGaN subregion 21 is electrically pumped.




Claims

1. A light-emitting diode chip comprising:

- a semiconductor body (1) having a plurality of active regions (2), wherein

- at least one of the active regions (2) has at least two subregions (21...28),

- the active region (2) has at least one barrier region (3) arranged between two adjacent subregions (21...28) of said at least two subregions (21...28),

- the at least two subregions (21...28) emit light of mutually different colour during operation of the light-emitting diode chip,

- in at least one of the subregions (21...28) the emission of light is generated electrically,

- the barrier region (3) is configured to hinder a thermally activated redistribution of charge carriers between the two adjacent subregions (21...28),

- the active regions (2) have a direction of main extension (R),

- at least some of the active regions (2) are spaced apart from each other in a direction (L) which runs lateral with respect to the direction of main extension (R) or at least some of the active regions (2) partly touch each other in the lateral direction,

- the active regions (2) are nanostructures and at least one of the active regions (2) has a maximum diameter of 1000 nm and a length in the direction of main extension of at least three times the maximum diameter,

- the subregions (21...28) are arranged along the direction of main extension (R) of their active region (2) and at least one barrier region (3) is arranged between each pair of adjacent subregions (21...28),

- each subregion (21...28) is based on a nitride compound semiconductor material comprising indium,

- each barrier region (3) is based on at least one nitride compound semiconductor material having a greater band gap than the subregions (21...28) adjoining the barrier region (3), and

each subregion (21...28) consists of one quantum well structure,
characterized in that
the barrier regions (3) are thinner in the direction of main extension (R) than the subregions (21...28) adjoining them.
 
2. The light-emitting diode chip according to the preceding claim, wherein

- each subregion (21...28) is based on an InGaN semiconductor material.


 
3. The light-emitting diode chip according to one of the preceding claims, wherein

- each barrier region (3) is based on GaN or AlInGaN or InGaN.


 
4. The light-emitting diode chip according to one of the preceding claims, wherein

- in at least two subregions (21...28) of the at least one active region (2) the emission of light is generated electrically, and

- a tunnel junction (6) is arranged between two electrically driven subregions (21...28).


 
5. The light-emitting diode chip according to the preceding claim, wherein

- the barrier region (3) between the two electrically driven subregions (21...28) is employed as the tunnel junction (6).


 
6. The light-emitting diode chip according to one of the preceding claims, wherein

- in at least one first subregion (21...28) of the at least one active region (2) the emission of light is generated electrically and in at least one second subregion (21...28) of the same active region (2) the emission of light is due to optically pumping by light of the first subregion (21...28).


 
7. The light-emitting diode chip according to the preceding claim, wherein

- the active region (2) forms a light-guide which guides the light of the at least one first subregion (21...28) along the direction of main extension (R) to the at least one second subregion.


 
8. The light-emitting diode chip according to one of the preceding claims, wherein

- at least one of the active regions (2) is configured to emit white light.


 


Ansprüche

1. Lichtemittierender Diodenchip, umfassend:

- einen Halbleiterkörper (1) mit einer Vielzahl von aktiven Bereichen (2), wobei

- zumindest einer der aktiven Bereiche (2) zumindest zwei Teilbereiche (21...28) aufweist,

- der aktive Bereich (2) mindestens einen Barrierebereich (3) aufweist, der zwischen zwei benachbarten Teilbereichen (21...28) der zumindest zwei Teilbereiche (21...28) angeordnet ist,

- die zumindest zwei Teilbereiche (21...28) im Betrieb des lichtemittierenden Diodenchips Licht mit voneinander unterschiedlicher Farbe emittieren,

- die Lichtemission in zumindest einem der Teilbereiche (21...28) elektrisch erzeugt wird,

- der Barrierebereich (3) dazu ausgebildet ist, um eine thermisch aktivierte Umverteilung von Ladungsträgern zwischen den beiden benachbarten Teilbereichen (21....28) zu verhindern,

- die aktiven Bereiche (2) eine Hauptstreckungsrichtung (R) aufweisen,

- zumindest einige der aktiven Bereiche (2) in einer Richtung (L) voneinander beabstandet sind, die in Bezug auf die Hauptstreckungsrichtung (R) lateral verläuft, oder zumindest einige der aktiven Bereiche (2) sich in der lateralen Richtung teilweise berühren,

- die aktiven Bereiche (2) Nanostrukturen sind und zumindest einer der aktiven Bereiche (2) einen maximalen Durchmesser von 1000 nm und eine Länge in der Hauptstreckungsrichtung von mindestens dem Dreifachen des maximalen Durchmessers aufweist,

- die Teilbereiche (21...28) entlang der Hauptstreckungsrichtung (R) ihres aktiven Bereichs (2) angeordnet sind und zwischen jedem Paar benachbarter Teilbereiche (21...28) zumindest ein Barrierebereich (3) angeordnet ist,

- jeder Teilbereich (21...28) auf einem Nitrid-Verbindungshalbleitermaterial basiert, das Indium umfasst,

- jeder Barrierebereich (3) auf zumindest einem Nitrid-Verbindungshalbleitermaterial mit einer größeren Bandlücke als die an den Barrierebereich (3) angrenzenden Teilbereiche (21...28) basiert, und

- jeder Teilbereich (21 .... 28) aus einer Quantentopfstruktur besteht,
dadurch charakterisiert, dass

- die Barrierebereiche (3) in Richtung der Hauptstreckungsrichtung (R) dünner sind als die angrenzenden Teilbereiche (21 .... 28).


 
2. Lichtemittierender Diodenchip nach dem vorhergehenden Anspruch, wobei

- jeder Teilbereich (21...28) auf einem InGaN-Halbleitermaterial basiert.


 
3. Lichtemittierender Diodenchip nach einem der vorhergehenden Ansprüche, wobei

- jeder Barrierebereich (3) auf GaN oder AlInGaN oder InGaN basiert.


 
4. Lichtemittierender Diodenchip nach einem der vorhergehenden Ansprüche, wobei

- in zumindest zwei Teilbereichen (21...28) des zumindest einen aktiven Bereichs (2) die Lichtemission elektrisch erzeugt wird, und

- ein Tunnelübergang (6) zwischen zwei elektrisch betriebenen Teilbereichen (21...28) angeordnet ist.


 
5. Lichtemittierender Diodenchip nach dem vorhergehenden Anspruch, wobei

- der Barrierebereich (3) zwischen den beiden elektrisch betriebenen Teilbereichen (21...28) als Tunnelübergang (6) verwendet wird.


 
6. Lichtemittierender Diodenchip nach einem der vorhergehenden Ansprüche, wobei

- in zumindest einem ersten Teilbereich (21...28) des zumindest einen aktiven Bereichs (2) die Lichtemission elektrisch erzeugt wird und in zumindest einem zweiten Teilbereich (21...28) des gleichen aktiven Bereichs (2) die Lichtemission durch optisches Pumpen mit Licht des ersten Teilbereichs (21...28) erfolgt.


 
7. Lichtemittierender Diodenchip nach dem vorhergehenden Anspruch, wobei

- der aktive Bereich (2) einen Lichtleiter bildet, der das Licht des zumindest einen ersten Teilbereichs (21...28) entlang der Haupterstreckungsrichtung (R) zum zumindest einen zweiten Teilbereich leitet.


 
8. Lichtemittierender Diodenchip nach einem der vorhergehenden Ansprüche, wobei

- zumindest einer der aktiven Bereiche (2) dazu ausgebildet ist weißes Licht zu emittieren.


 


Revendications

1. Puce de diode électroluminescente comprenant:

- un corps semi-conducteur (1) ayant une pluralité de régions actives (2), dans lequel

- au moins une des régions actives (2) comporte au moins deux sous-régions (21...28),

- la région active (2) comporte au moins une région barrière (3) disposée entre deux sous-régions (21...28) adjacentes des au moins deux sous-régions (21...28),

- les au moins deux sous-régions (21...28) émettent une lumière de couleur mutuellement différente pendant le fonctionnement de la puce de diode électroluminescente,

- dans au moins une des sous-régions (21...28), l'émission de lumière est produite électriquement,

- la région barrière (3) est configurée pour empêcher une redistribution thermiquement activée des porteurs de charge entre les deux sous-régions (21...28) adjacentes,

- les régions actives (2) ont une direction d'extension principale (R),

- au moins certaines des régions actives (2) sont espacées l'une de l'autre dans une direction (L) qui s'étend latéralement par rapport à la direction d'extension principale (R) ou au moins certaines des régions actives (2) sont en contact partiel dans la direction latérale,

- les régions actives (2) sont des nanostructures et au moins une des régions actives (2) a un diamètre maximum de 1000 nm et une longueur dans la direction d'extension principale d'au moins trois fois le diamètre maximum,

- les sous-régions (21...28) sont disposées dans le sens d'extension principale (R) de leur région active (2) et au moins une région barrière (3) est disposée entre chaque paire de sous-régions (21...28) adjacentes,

- chaque sous-région (21...28) est basée sur un matériau semi-conducteur composé de nitrure comprenant de l'indium,

- chaque région barrière (3) est basée sur au moins un matériau semi-conducteur composé de nitrure ayant une bande interdite plus grande à celle des sous-régions (21...28) adjacentes à la région barrière (3), et

- chaque sous-région (21... 28) est constituée d'une structure à puits quantiques,
caractérisé en ce que

- les régions barrières (3) sont plus minces dans la direction de la direction d'extension principale (R) que les sous-régions (21.... 28) adjacentes.


 
2. Puce de diode électroluminescente selon la revendication précédente, dans laquelle

- chaque sous-région (21...28) est basée sur un matériau semi-conducteur InGaN.


 
3. Puce de diode électroluminescente selon l'une des revendications précédentes, dans laquelle

- chaque région barrière (3) est basée sur le GaN ou l'AlInGaN ou l'InGaN.


 
4. Puce de diode électroluminescente selon l'une des revendications précédentes, dans laquelle

- dans au moins deux sous-régions (21...28) de la au moins une région active (2), l'émission de lumière est produite électriquement, et

- une jonction tunnel (6) est disposée entre deux sous-régions (21...28) à commande électrique.


 
5. Puce de diode électroluminescente selon la revendication précédente, dans laquelle

- la région barrière (3) entre les deux sous-régions (21...28) à commande électrique est utilisée comme jonction tunnel (6).


 
6. Puce de diode électroluminescente selon l'une des revendications précédentes, dans laquelle

- dans au moins une première sous-région (21...28) de la au moins une région active (2), l'émission de lumière est produite électriquement et dans au moins une deuxième sous-région (21...28) de la même région active (2), l'émission de lumière est due au pompage optique de la lumière de la première sous-région (21...28).


 
7. Puce de diode électroluminescente selon la revendication précédente, dans laquelle

- la région active (2) forme un guide de lumière qui guide la lumière de la au moins une première sous-région (21...28) dans la direction d'extension principale (R) vers la au moins une seconde sous-région.


 
8. Puce de diode électroluminescente selon l'une des revendications précédentes, dans laquelle

- au moins l'une régions actives (2) est configurée pour émettre une lumière blanche.


 




Drawing


















REFERENCES CITED IN THE DESCRIPTION



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Patent documents cited in the description




Non-patent literature cited in the description