RADIATION-EMITTING SEMICONDUCTOR CHIP AND METHOD FOR MANUFACTURING A RADIATION-EMITTING SEMICONDUCTOR CHIP

Abstract

In an embodiment a radiation-emitting semiconductor chip includes a first doped region, an active region adjacent to the first doped region and a second doped region arranged on a side of the active region facing away from the first doped region, wherein the first doped region is structured in a step-like manner and includes several planes in a direction perpendicular to a main extension plane of the semiconductor chip, and wherein the active region covers the first doped region on a side surface and a top surface.

Claims

1.-13. (canceled)

14. A radiation-emitting semiconductor chip comprising: a first doped region; an active region adjacent to the first doped region, the active region configured to generate electromagnetic radiation; and a second doped region arranged on a side of the active region facing away from the first doped region, wherein the first doped region is structured in a step-like manner and comprises several planes in a direction perpendicular to a main extension plane of the radiation-emitting semiconductor chip, and wherein the active region covers the first doped region on a side surface and a top surface.

15. The radiation-emitting semiconductor chip according to claim 14, wherein the active region completely covers the side surface of the first doped region.

16. The radiation-emitting semiconductor chip according to claim 14, wherein the first doped region is arranged on a substrate, and wherein the substrate comprises a flat top surface on the side facing the first doped region.

17. The radiation-emitting semiconductor chip according to claim 14, wherein the first doped region comprises a three-dimensional shape, and wherein the shape of the first doped region is approximated to a shape of a step pyramid.

18. The radiation-emitting semiconductor chip according to claim 14, wherein the radiation-emitting semiconductor chip comprises the main extension plane, wherein the active region extends obliquely to the main extension plane in places.

19. The radiation-emitting semiconductor chip according to claim 14, wherein the active region is curved.

20. The radiation-emitting semiconductor chip according to claim 14, wherein the first doped region tapers along the direction perpendicular to the main extension plane of the radiation-emitting semiconductor chip.

21. The radiation-emitting semiconductor chip according to claim 14, further comprising a first contact electrically conductively connected to the first doped region, wherein the first contact extends into the first doped region.

22. The radiation-emitting semiconductor chip according to claim 14, wherein the radiation-emitting semiconductor chip comprises an edge length less than or equal to 20 m.

23. The radiation-emitting semiconductor chip according to claim 14, further comprising a non-planar radiation outcoupling surface, wherein the active region is non-planar.

24. A method for manufacturing a radiation-emitting semiconductor chip, the method comprising: providing a substrate; depositing a first doped region; structuring the first doped region such that the first doped region is structured in a step-like manner and tapers along a direction away from the substrate and comprises several planes; depositing an active region such that the active region covers a side surface of the first doped region; and depositing a second doped region on the active region.

25. The method according to claim 24, wherein structuring comprises multiple etching.

26. The method according to claim 24, wherein a part of the active region is deposited prior to a first deposition of the first doped region and the second doped region.

27. The method according to claim 26, wherein the active region is removed partially prior to a deposition of the first doped region and the second doped region taking place.

28. A radiation-emitting semiconductor chip comprising: a first doped region; an active region adjacent to the first doped region, the active region configured to generate electromagnetic radiation; and a second doped region arranged on a side of the active region facing away from the first doped region, wherein the first doped region is structured in a step-like manner and comprises several planes in a direction perpendicular to a main extension plane of the radiation-emitting semiconductor chip, wherein the active region covers the first doped region on a side surface and a top surface, and wherein the first doped region comprises a three-dimensional shape, the shape of the first doped region being approximated to a shape of a step pyramid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] With reference to the schematic sectional views of FIGS. 1A to 1D, a first exemplary embodiment of a method described herein is explained in more detail.

[0060] With reference to the schematic sectional views of FIGS. 2 and 3, exemplary embodiments of a radiation-emitting semiconductor chip described herein are explained in more detail.

[0061] With reference to the perspective schematic views of FIGS. 4A and 4B, a further exemplary embodiment of a radiation-emitting semiconductor chip described herein is explained in more detail.

[0062] With reference to the schematic views of FIGS. 5A to 5D, a further exemplary embodiment of a method described herein is explained in more detail.

[0063] With reference to the schematic sectional view of FIG. 6, a further exemplary embodiment of a radiation-emitting semiconductor chip described herein is explained in more detail.

[0064] With reference to the schematic sectional views of FIGS. 7A to 7D as well as FIGS. 8A to 8E, further exemplary embodiments of a method described herein are explained in more detail.

[0065] With reference to the schematic views of FIGS. 9 and 10, further exemplary embodiments of radiation-emitting semiconductor chips described herein are explained in more detail.

[0066] With reference to the schematic views of FIGS. 11A to 11F, the operation of a radiation-emitting semiconductor chip described herein is explained in more detail.

[0067] Elements that are identical, similar or have the same effect are given the same reference signs in the figures. The figures and the proportions of the elements shown in the figures are not to be regarded as to scale. Rather, individual elements may be shown exaggeratedly large for better representability and/or for better comprehensibility.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0068] In connection with the schematic sectional views of FIGS. 1A to 1D, a first exemplary embodiment of a method described herein is explained in more detail. In the method, a substrate 1 is provided.

[0069] On the substrate 1 a first doped region 2 is deposited. The first doped region 2 is, for example, a region formed with a p-doped semiconductor material.

[0070] Subsequently, a structuring of the first doped region 2 takes place so that it is formed trapezoidal in a cross-section perpendicular to a main extension plane L of the semiconductor chip 10, as shown schematically in FIG. 1A. The first region 2 structured in this way tapers in a direction R away from the substrate 1.

[0071] The first doped region 2 then comprises side surfaces 2a that run transversely to the main extension plane L. Furthermore, the first doped region 2 comprises a top surface 2b that runs in parallel to the main extension plane L.

[0072] After the first doped region 2 is structured and prepared for an overgrowth, an overgrowth takes place by deposition of an active region 3, such that the active region covers a side surface 2a of the first doped region 2.

[0073] In the present case, the active region 3 completely and conformally covers the side surfaces 2a as well as the top surface 2b of the first doped region 2. This is shown in FIG. 1B.

[0074] For overgrowth with the active region, the side surfaces 2a of the first doped region are preferably group V-terminated. In this way, the active region can be grown with particularly good crystal quality on the top surface 2b, which runs parallel to the (001)-crystal plane, for example, and in side surfaces 2a.

[0075] In a next method step, FIG. 1C, the lateral regions of the active region 3 are removed, such that only regions of the active region 3 remain, which are located on a side surface 2a and the top surface 2b of the first doped region 2.

[0076] For this, a corresponding mask 5 can be applied. The mask 5 can be formed with SiNx, SiON or SiO2, for example, and applied by means of an ALD method, for example. The removal of the active region 3 in the region not covered by the mask 5 takes place, for example, by means of dry- or wet-chemical etching.

[0077] In the next method step, FIG. 1D, the deposition of a second doped region 4 on the active region 3 is performed. The second doped region 4 is formed, for example, by an n-doped semiconductor material.

[0078] This results in a radiation-emitting semiconductor chip 10 as schematically shown in FIG. 1D, wherein the first region 2 is structured and the active region covers the first doped region 2 at the side surfaces 2a and a top surface 2b.

[0079] The radiation-emitting semiconductor chip 10 can thereby, as shown in FIG. 1D, comprise a first doped region with exactly one top surface 2b, which runs parallel to the main extension plane L of the semiconductor chip 10. Thereby, the structure size of the structuring of the first doped region 2 corresponds approximately to the edge length x of the radiation-emitting semiconductor chip 10. In other words, the first doped region 2 comprises, at its bottom surface 2c facing away from the top surface 2b, a lateral extension which corresponds to at least 20%, in particular at least 50% or at least 80% of the edge length x of the semiconductor chip 10.

[0080] The schematic sectional view of FIG. 2 shows a further exemplary embodiment of a radiation-emitting semiconductor chip 10 described herein. In this exemplary embodiment, compared to the exemplary embodiment of FIG. 1D, the size of the top surface 2b of the first doped region 2 is reduced. In this way, the shape of the active region 3 corresponds more to the shape of a semicircle than is the case, for example, for the exemplary embodiment of FIG. 1D. The probability of a total reflection when leaving the radiation-emitting semiconductor chip 10 is thus further reduced and the efficiency of the semiconductor chip 10 is increased, but the area of the active region 3 is reduced compared to the exemplary embodiment of FIG. 1D.

[0081] The schematic sectional view of FIG. 3 shows a further exemplary embodiment of a radiation-emitting semiconductor chip 10 described herein. In contrast to the exemplary embodiment of FIGS. 2 and 1D, in the exemplary embodiment of FIG. 3, the contacts 7 and 8 for external contacting of the radiation-emitting semiconductor chip 10 are now added. Thereby, the first contact 7 extends at least through the substrate 1 and/or an epitaxially grown layer. The second contact 8 is applied on the second doped region 4, for example, as a radiation-transmissive contact. The second contact 8 can be, for example, a contact which is formed with a TCO-material such as ITO, for example. The outer surface of the second contact 8 forms the radiation outcoupling surface 10a of the semiconductor chip 10.

[0082] The schematic perspective views of FIGS. 4A and 4B show further exemplary embodiments of a radiation-emitting semiconductor chip 10 described herein. In these exemplary embodiments, the semiconductor chip 10 extends longer in one spatial direction than in the other spatial direction. That is, the semiconductor chip 10 comprises an edge length x and a further edge length y, wherein the further edge length y is large relative to the edge length x.

[0083] The radiation-emitting semiconductor chip 10 thus has a strip-shaped extension and the area of the portions of the active region 3, which are applied on side surfaces 2a of the first doped region 2, is particularly large compared to the area of the top surface 2b.

[0084] Thus, on the one hand, the probability of a total reflection when electromagnetic radiation exits the semiconductor chip 10 is reduced, and on the other hand, the probability of non-radiative recombination at the surface is also reduced.

[0085] If the semiconductor chip 10 is formed in the InGaAlP material system, for example, the oblique regions of the active region 3 are oriented parallel to the (111) x-facet, wherein x=A and B can be. For other material systems, other facets can be advantageous.

[0086] As shown in FIG. 4B, the semiconductor chip 10 can be bounded in both lateral directions by side surfaces 2a. Such a 3D-geometry leads to an even stronger suppression of non-radiative recombination. The size of the semiconductor chip 10 is tunable, the emission perpendicular to the outcoupling surface 10a is maximized, the area for breaking up of total reflection is maximized, resulting in increased efficiency. Substrate and contacts are not shown in FIG. 4B.

[0087] Overall, a radiation-emitting semiconductor chip 10 described herein is characterized by improved radiation outcoupling efficiency because a particularly large amount of electromagnetic radiation is incident perpendicular to the radiation outcoupling surface 10a and the probability of non-radiative recombination is also reduced.

[0088] In connection with the schematic views of FIGS. 5A to 5D, a further exemplary embodiment of a method described herein is explained in more detail. In this exemplary embodiment, the first doped region 2 is structured in a step-like manner by multiple overgrowth, as shown in FIGS. 5A and 5B, so that the first doped region 2 comprises a plurality of planes 21, 22, 23 in the direction R, which is, for example, perpendicular to the main extension plane L.

[0089] In the next method step, FIG. 5C, the active region 3 is then conformally deposited so that it comprises corresponding sections 31, 32, 33 along the planes 21, 22, 23 which are oblique to the main extension plane L.

[0090] The second doped layer 4 is correspondingly conformally deposited over the active region 3, FIG. 5D.

[0091] Thus, an embodiment of the radiation-emitting semiconductor chip 10 can be realized as shown in idealized form in FIG. 6. There, the first doped region 2 is hemispherical structured and the active region 3 is correspondingly conformally applied to the first doped region 2. Electromagnetic radiation 9 generated in the active region 3 then strikes the outer surface of the semiconductor chip 10 largely perpendicularly and can be emitted without significant total reflection. This results in a theoretical radiation outcoupling efficiency of 69.6% compared to a radiation outcoupling efficiency of only about 14% for a planar active region. Thereby, it is assumed that the semiconductor material of the second doped region comprises a refractive index of 3 and that the substrate 1 is formed to be reflective, for example as a Bragg reflector. Further, the radiation outcoupling surface 10a is curved conformally to the outer surface of the active region 3, which faces the radiation outcoupling surface 10a.

[0092] In connection with the schematic sectional views of FIGS. 7A to 7D, a further exemplary embodiment of a method described herein is explained in more detail.

[0093] In this exemplary embodiment, the first doped region 2 is subsequently etched using different masks 5 so that also a step-like or step-shaped profile results with planes 21 to 25 of the first doped region 2. In this way, different geometries are possible for the first doped region 2 depending on the mask used, for example the shape of a step pyramid or an approximated hemisphere.

[0094] The etching steps are shown in connection with FIGS. 7B and 7C.

[0095] In FIG. 7D, it is shown that in each plane sections 31 to 35 of the active region 3 are arranged, which each extend to the side surface 2a in each plane of the first doped region 2. Subsequently, a second doped region 4 can be applied correspondingly (not shown).

[0096] In connection with the schematic views of FIGS. 8A to 8E, a further exemplary embodiment of a method described herein is explained in more detail. In this exemplary embodiment, as in the exemplary embodiment of FIGS. 7A to 7D, the active layer 3 is grown only in the (001)-plane, by which a technically particularly simple growth process is possible.

[0097] First, the active region 3 is deposited over a large area on the substrate 1, FIG. 8A.

[0098] Subsequently, a part of the active region 3 is removed by etching, such that only a ring on the substrate 1 remains, which is formed with material of the active region 3.

[0099] Onto the exposed regions of the substrate 1, the first doped region 2 inside the ring and the second doped region 4 outside the ring are subsequently deposited. This is shown in FIG. 8C.

[0100] This method is repeated for progressively smaller diameters of ring-shaped active regions 3, FIG. 8D.

[0101] The doped regions 2, 4 as well as the active regions 3 can be deposited via a MOCVD-process, wherein growth masks formed with silicon dioxide or silicon nitride come into use.

[0102] Subsequently, a first contact 7 is generated either through the substrate 1, FIG. 8 E, or the substrate 1 is detached and the first contact 7 is generated (not shown).

[0103] Optoelectronic semiconductor chips 10 as schematically shown in FIGS. 9 and 10 result, wherein a hemispherical design of the outer surface of the active region 3 can be achieved by as many epitaxial steps as possible. In the center of the first doped region 2, the first contact 7 extends into the first doped region 2.

[0104] In connection with the schematic views of FIGS. 11A to 11F, the operation of radiation-emitting semiconductor chips 10 described herein is explained in more detail.

[0105] FIG. 11A shows a radiation-emitting semiconductor chip 10 with a flat radiation outcoupling surface 10a. High refractive indices of the semiconductor material of the radiation-emitting semiconductor chip 10 result in a small extraction cone of the emitted radiation, as shown in FIG. 11A. A small extraction cone hinders emission from the active region 3.

[0106] FIG. 11B shows that by introducing a curved radiation outcoupling surface 10a such as would result for a semiconductor chip 10 described herein, the extraction cone is greatly enlarged.

[0107] FIG. 11C shows the radiation from the edge of a radiation-emitting semiconductor chip 10 with a flat radiation outcoupling surface 10a.

[0108] FIG. 11D shows that by introducing a curved radiation outcoupling surface 10a, the emission that occurs from the edge of the active region 3 does not benefit as much from the improved extraction cone as the emission from the center of the semiconductor chip 10.

[0109] FIG. 11E shows emission from a radiation-emitting semiconductor chip 10 with a flat radiation outcoupling surface 10a and a flat active region 3.

[0110] FIG. 11F shows that due to the curvature of the active region the problem of emission from the edge of the active region 3 is solved. At the same time, the curved radiation outcoupling surface 10a results in an improved extraction cone with an increased aperture angle.

[0111] The invention is not limited by the description given with reference to the embodiments. Rather, the invention encompasses any novel feature as well as any combination of features, which in particular includes any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or embodiments.