Growth structure for a radiation-emitting semiconductor component, and radiation-emitting semiconductor component

Abstract

In an embodiment a growth structure for a radiation-emitting semiconductor component includes a semiconductor substrate containing a material based on arsenide compound semiconductors and a buffer structure arranged on the semiconductor substrate, wherein the buffer structure includes a buffer layer having at least one n-doped layer and wherein the n-doped layer contains oxygen, and a molar fraction of oxygen in the n-doped layer is between 10.sup.15 cm.sup.3 and 10.sup.19 cm.sup.3, inclusive.

Claims

1. A growth structure for a radiation-emitting semiconductor component comprising: a semiconductor substrate containing a material based on arsenide compound semiconductors; and a buffer structure, which is arranged on the semiconductor substrate and contains a material based on arsenide compound semiconductors, wherein the buffer structure comprises: a first buffer layer comprising at least one n-doped layer, wherein the n-doped layer contains a material based on arsenide compound semiconductors and oxygen, and a molar fraction of oxygen in the n-doped layer is between 10.sup.15 cm.sup.3 and 10.sup.19 cm.sup.3, and at least one second buffer layer, which contains a material based on arsenide compound semiconductors, is n-doped and contains oxygen, wherein the second buffer layer is configured to serve as an etch stop layer when the semiconductor substrate or the growth structure is detached from a luminescent diode structure, and wherein one of the first buffer layer or the second buffer layer is a bulk layer and the other one consists of a superlattice.

2. The growth structure according to claim 1, wherein the semiconductor substrate comprises dislocation lines which continue into the buffer structure and are kinked by the first buffer layer.

3. The growth structure according to claim 1, wherein the at least one n-doped layer contains AlGaAsO.

4. The growth structure according to claim 3, wherein the at least one n-doped layer contains AlmGa1mAs:O and 0.01m1.

5. The growth structure according to claim 1, wherein the at least one n-doped layer consists of n-doped AlGaAsO.

6. The growth structure according to claim 1, wherein the molar fraction of oxygen in the n-doped layer is at least 100 ppm and at most 20,000 ppm.

7. The growth structure according to claim 1, wherein the first buffer layer consists of an n-doped oxygen-containing layer.

8. The growth structure according to claim 1, wherein the first buffer layer comprises at least one n-doped oxygen-free layer and at least one n-doped oxygen-containing layer arranged one on top of the other.

9. The growth structure according to claim 8, wherein the first buffer layer comprises a plurality of n-doped oxygen-free layers and a plurality of n-doped oxygen-containing layers arranged alternately.

10. The growth structure according to claim 8, wherein the at least one oxygen-free layer has a thickness between 0.5 nm and 10 nm, inclusive.

11. The growth structure according to claim 8, wherein the at least one oxygen-containing layer has a thickness between 0.5 nm and 5 nm, inclusive.

12. The growth structure according to claim 8, wherein the oxygen-free layer contains GaAs.

13. The growth structure according to claim 1, wherein the semiconductor substrate consists of GaAs.

14. The growth structure according to claim 1, wherein the buffer structure comprises at least one further buffer layer, which is n-doped and free of oxygen.

15. The radiation-emitting semiconductor component comprising: the growth structure according to claim 1; and the luminescent diode structure based on arsenide or phosphide compound semiconductors and having a first region of a first conductivity type, a second region of a second conductivity type, and an active region arranged between the first and second regions, the active region configured to generate radiation, wherein the luminescent diode structure is grown onto the growth structure.

16. The radiation-emitting semiconductor component according to claim 15, wherein the radiation-emitting semiconductor component is free of a transistor structure or a thyristor structure between the buffer structure and the active region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, preferred embodiments and further developments of the growth structure as well as of the radiation-emitting semiconductor component will become apparent from the following explanations in connection with FIGS. 1 to 4.

(2) FIG. 1 shows a schematic view of a TEM image of a conventional semiconductor structure based on nitride compound semiconductors (source: dissertation Metallorganische Gasphasen-Epitaxie von Gruppe III-Nitrid-basierten LED Strukturen auf Silizium (Metal-Organic Vapor Phase Epitaxy of Group III Nitride-based LED Structures on Silicon), page 136, FIG. 5.36, 1982 Jul. 7, Sebastian Drechsel);

(3) FIG. 2 shows a schematic cross-sectional view of a radiation-emitting semiconductor component according to a comparative example;

(4) FIG. 3 shows a schematic cross-sectional view of a radiation-emitting semiconductor component according to a first embodiment; and

(5) FIG. 4 shows a schematic cross-sectional view of a radiation-emitting semiconductor component according to a second embodiment.

(6) Elements that are identical, similar or have the same effect are given the same reference signs in the figures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(7) FIGS. 1 to 4 are each schematic representations and therefore not necessarily drawn to scale. Rather, comparatively small elements and, in particular, layer thicknesses may be shown exaggeratedly large for clarification purposes.

(8) FIG. 1 shows a conventional semiconductor structure 15 based on nitride compound semiconductors.

(9) Based on nitride compound semiconductors in the present context means that the active epitaxial layer sequence or at least one layer thereof comprises a nitride III/V compound semiconductor material.

(10) The semiconductor structure 15 comprises a growth structure 1 and a semiconductor layer sequence 17 grown thereon. The growth structure 1 comprises a semiconductor substrate 2 and an ELOG (Epitaxial Lateral Overgrowth) masking layer 16 deposited on the semiconductor substrate 2. The ELOG masking layer 16 is provided to reduce the dislocation density in the semiconductor structure 15. The masking layer 16 is formed of SiN, while the semiconductor substrate 2 consists of sapphire.

(11) The ELOG masking layer 16 has a plurality of recesses (not marked) through which the semiconductor layer sequence 17 is formed on the semiconductor substrate 2 by epitaxial growth. Since dislocations can only propagate through the recesses, the growth structure 1 has a reduced dislocation density on a side facing the semiconductor layer sequence 17 compared to the semiconductor substrate 2.

(12) As can be seen from FIG. 1, breakthroughs 18 of impurities nevertheless occur. In addition, the production of the recesses in the ELOG masking layer 16, for example by photolithographic structuring, is comparatively costly.

(13) FIG. 2 shows a comparative example of a radiation-emitting semiconductor component 10. The radiation-emitting semiconductor component 10 comprises a growth structure 1 and a luminescent diode structure 11 arranged thereon for generating radiation, preferably in the infrared range.

(14) The growth structure 1 comprises a semiconductor substrate 2 made of GaAs with a comparatively high dislocation density. To reduce the dislocation density, the growth structure 1 includes a buffer layer 4 which is arranged on the semiconductor substrate 2 and on which the luminescent diode structure 11 is grown.

(15) The buffer layer 4 is an n-doped layer of GaAs which is free of oxygen. For example, tellurium is used as the n-dopant.

(16) The luminescent diode structure 11 is deposited on the growth structure 1. The luminescent diode structure 11 contains materials based on arsenide compound semiconductors. Adjacent to the growth structure 1, the luminescent diode structure 11 comprises a first, n-type region 12 followed in a growth direction A by an active region 13 for generating radiation. The active region 13 is followed in the growth direction A by a second, p-type region 14.

(17) The buffer layer 4 included in the growth structure 1 can be formed largely without dislocations. However, the buffer layer 4 cannot sufficiently prevent migration of the dislocation lines 7 from the semiconductor substrate 2 into the luminescent diode structure 11 during growth of the luminescent diode structure 11 or later during operation of the component. As shown in FIG. 2, the dislocation lines 7 extend from the semiconductor substrate 2 through the first region 12 and the active region 13 into the second region 14, thereby degrading the crystal quality of the radiation-emitting semiconductor component 10.

(18) Overall, therefore, neither the masking layer 16 described in connection with FIG. 1 nor the buffer layer 4 described in connection with FIG. 2 can achieve a sufficiently high crystal quality at an acceptable manufacturing cost.

(19) The situation is different in the embodiments described below in connection with FIGS. 3 and 4.

(20) The radiation-emitting semiconductor component 10 shown in FIG. 3 comprises a growth structure 1 and a luminescent diode structure 11 arranged thereon for generating radiation.

(21) The growth structure 1 is a composite component comprising a semiconductor substrate 2 and a buffer structure 3 arranged on the semiconductor substrate 2. In particular, the semiconductor substrate 2 forms a growth substrate suitable for both growing the buffer structure 3 and growing the luminescent diode structure 11. Furthermore, the semiconductor substrate 2 advantageously forms a self-supporting stable base body and can serve as a carrier body in the finished radiation-emitting semiconductor component 10. Alternatively, the semiconductor substrate 2 can be removed or at least thinned and, for example, be replaced by another carrier.

(22) Both the semiconductor substrate 2 and the buffer structure 3 are formed of materials based on arsenide compound semiconductors. Preferably, the semiconductor substrate 2 is made of GaAs.

(23) The luminescent diode structure 11, too, may contain materials based on arsenide compound semiconductors. Alternatively, the luminescent diode structure 11 may contain materials based on phosphide compound semiconductors.

(24) Suitable methods for producing the buffer and luminescent diode structures 3, 11 include MOCVD (Metal-Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or LPE (Liquid Phase Epitaxy).

(25) In the embodiment shown in FIG. 3, the buffer structure 3 consists of a buffer layer 4 which comprises a superlattice. The buffer layer 4 comprises several n-doped, oxygen-free layers 6 and several n-doped, oxygen-containing layers 5, which are arranged on top of each other in alternating sequence. In particular, AlGaAsO is suitable as a material system for the oxygen-containing layers 5. In this case, a molar fraction of aluminum is preferably between 1% and 100% inclusive, in particular between 1% and 60% inclusive. In other words, the n-doped oxygen-containing layers 5 each contain Al.sub.mGa.sub.1-mAs:O, where 0.01m1, particularly preferably 0.01m0.6. Preferably, the molar fraction of oxygen is greater than 10.sup.15 cm.sup.3 and is at most 10.sup.19 cm.sup.3. Particularly preferably, the molar fraction of oxygen in the n-doped layers 5 is between 10.sup.17 cm.sup.3. In other words, the molar fraction can be at least 100 ppm and at most 20,000 ppm. GaAs is particularly suitable for the oxygen-free layers 6. Deviations of up to 10% are quite tolerable for the indicated molar fractions. The same n-dopant can be used for doping both the oxygen-containing and the oxygen-free layers 6, 5.

(26) The oxygen-free layers 6 preferably have a thickness D1 between and including 0.5 nm, preferably 2 nm, and 10 nm. Furthermore, the thickness D2 of the oxygen-containing layers 5 is in particular between 0.5 nm, preferably 1 nm, and 5 nm. Deviations of up to 10% are quite tolerable.

(27) The luminescent diode structure 11 comprises a first region 12 of a first conductivity type, a second region 14 of a second conductivity type, and an active region 13 arranged between the first and second regions 12, 14 for generating radiation. Preferably, the first region 12 is an n-type conductive region and the second region 14 is a p-type conductive region. Furthermore, the first region 12 is arranged on a side of the active region 13 facing the growth structure 1, while the second region 14 is arranged on a side of the active region 13 facing away from the growth structure 1.

(28) As can be seen in FIG. 3, dislocation lines 7 extend from the semiconductor substrate 2 into the buffer structure 3 or buffer layer 4.

(29) By means of the buffer structure 3 or buffer layer 4, the dislocation lines 7 are largely kinked so that they do not migrate further into the luminescent diode structure 11. The inventors have found that in particular the oxygen used in the n-doped layers 5 causes the dislocation lines to kink so that they cannot for the most part penetrate into the luminescent diode structure 11.

(30) This effect can also be achieved with a buffer structure 3 that does not consist of only one buffer layer 4 as in the illustrated exemplary embodiment, but comprises at least one further buffer layer (not shown). A further buffer layer may be arranged on a side of the buffer layer 4 facing the semiconductor substrate 2 or on a side of the buffer layer 4 facing away from the semiconductor substrate 2. Two further buffer layers may also be provided, in which case the buffer layer 4 is arranged between them. The at least one further buffer layer may contain GaAs, be free of oxygen and furthermore be n-doped. For example, tellurium can be used as the n-dopant. Furthermore, it is conceivable that the at least one further buffer layer is designed as a bulk layer with the properties described below in connection with FIG. 4.

(31) The radiation-emitting semiconductor component 10 is designed as a laser diode which, in particular, emits radiation in the infrared range with a wavelength between 750 nm and 1200 nm. Furthermore, the radiation-emitting semiconductor component 10 shown is an edge emitter which emits the radiation generated by the active region 13 at a side surface of the semiconductor component 10 arranged parallel to the image plane. The side surfaces 10A as well as the side surfaces arranged parallel to the image plane (not shown) limit the semiconductor component 10 in lateral directions, i.e. in directions extending transversely, in particular perpendicularly, to a growth direction A of the luminescent diode structure. The growth direction A indicates the direction in which the regions 12, 13, 14 of the luminescent diode structure 11 are successively applied to the growth structure 1.

(32) In particular, the radiation-emitting component 10 is a high power laser diode that yields a radiation output of from 20 W to 300 W, inclusive, at a current of between 20 A and 300 A. To achieve such a radiation output, the luminescent diode structure 11 of the semiconductor component 10 may be in the form of a laser bar, comprising a plurality of adjacent strip-like regions each having a structure as shown in FIG. 3.

(33) The exemplary embodiment of a radiation-emitting semiconductor component 10 shown in FIG. 4 has a similar structure to that of the semiconductor component 10 shown in FIG. 3. In this respect, reference is made to the explanations given above. Differences exist in the buffer structure 3, which will be discussed in more detail below.

(34) The radiation-emitting semiconductor component 10 comprises a growth structure 1 and a luminescent diode structure 11 arranged thereon for generating radiation. Both structures 1, 11 may contain materials based on arsenide compound semiconductors. Alternatively, the luminescent diode structure 11 may be formed of materials based on phosphide compound semiconductors.

(35) The growth structure 1 comprises a semiconductor substrate 2, preferably a GaAs substrate, and a buffer structure 3 grown in particular on the semiconductor substrate 2.

(36) The buffer structure 3 comprises a first buffer layer 4 consisting of an n-doped, oxygen-containing layer 5. The buffer layer 4 has AlGaAs as the material system, which is oxygenated. The buffer layer 4 is thus formed from AlGaAsO. The buffer layer 4 is a so-called bulk layer. In other words, the buffer layer 4 is largely homogeneous, i.e. made of only one material system, and is comparatively thick or stable.

(37) In the exemplary embodiment shown in FIG. 4, the buffer structure 3 comprises two further buffer layers 8, 9, between which the first buffer layer 4 is arranged. In this case, the first buffer layer 4 can be formed comparatively thin with a thickness D of about 10 nm.

(38) The second and third buffer layers 8, 9 can each contain GaAs and be n-doped, with tellurium being used as the n-dopant, for example. In particular, the buffer layers 8, 9 are free of oxygen. Alternatively, the second and third buffer layers 8, 9 can each consist of a superlattice as described in connection with the buffer layer 4 shown in FIG. 3.

(39) Furthermore, it is conceivable that the buffer structure 3 comprises only one further buffer layer, which is arranged on a side of the first buffer layer 4 facing towards or away from the semiconductor substrate 2.

(40) It is also possible for the buffer structure 3 to consist only of the buffer layer 4. In this case, the buffer layer 4 is comparatively thick with a preferred thickness D of between 50 nm and 150 nm inclusive, with deviations of up to 10% being tolerable.

(41) The radiation-emitting component 10 is preferably an edge-emitting laser diode having the characteristics already described in connection with FIG. 3. However, the radiation-emitting semiconductor component 10 may also be a surface-emitting laser diode in which the radiation is coupled out at a main surface 10B of the semiconductor component 10.

(42) Overall, the crystal quality of the luminescent diode structures 11 can be improved by means of the buffer structures 3 described herein, so that fewer failures occur in the semiconductor components 10 and the operating life can be extended.

(43) The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments.