Patent Application
20240136176
A growth substrate for the epitaxial growth of an epitaxial semiconductor layer sequence based on a semiconductor compound material and a method for manufacturing an optoelectronic semiconductor body are provided.
Embodiments provide a growth substrate for epitaxial growth of an epitaxial semiconductor layer sequence based on a semiconductor compound material, wherein an improved crystal quality of the epitaxial semiconductor layer sequence can be achieved.
Further embodiments provide a method for manufacturing a semiconductor body having an epitaxial semiconductor layer sequence based on a semiconductor compound material, the epitaxial semiconductor layer sequence having an improved crystal quality.
According to an embodiment, the growth substrate is configured for epitaxial growth of an epitaxial semiconductor layer sequence based on a semiconductor compound material. In particular, a semiconductor compound material is a chemical compound of at least two different chemical elements.
According to a further embodiment of the growth substrate, the semiconductor compound material is a III/V semiconductor compound material. In other words, the semiconductor layer sequence can comprise a III/V semiconductor compound material or can consist of a III/V semiconductor compound material. A III/V semiconductor compound material comprises group III elements GIII(1), GIII(2), GIII(3) and a group V element GV and has the general formula GIII(1)xGIII(2)yGIII(3)1-x-yGV with 0≤x≤1, 0≤y≤1 and x+y≤1.
According to a further embodiment of the growth substrate, the semiconductor compound material is a II/VI semiconductor compound material. In other words, the semiconductor layer sequence can comprise a II/VI semiconductor compound material or can consists of a II/VI semiconductor compound material.
A II/VI semiconductor compound material comprises group II elements and/or group XII elements GII(1), GII(2) and group VI elements GVI(1), GVI(2). Particularly, a II/VI semiconductor compound material can be a binary compound with the chemical formula (GII(1)GVI(1)) or a ternary compound with the chemical formula GII(1)(GVI(1),GVI(2)) or (GII(1),GVI(1))GVI(2).
According to a further embodiment, the growth substrate comprises a substrate. For example, the substrate is responsible for the mechanical stability of the growth substrate. In particular, the substrate is thicker than a buffer layer sequence. Further, the substrate is preferably a single crystal and not epitaxial grown.
According to a further embodiment, the growth substrate comprises a buffer layer sequence. The buffer layer sequence comprises at least one semiconductor layer and at least one buffer layer. The semiconductor layer is based on a semiconductor compound material or consists of a semiconductor compound material.
Preferably, the semiconductor layer is based on a semiconductor compound material from the same material system as the epitaxial semiconductor layer sequence to be grown on the growth substrate or consists of a semiconductor compound material of the same material systems as the epitaxial semiconductor layer sequence to be grown on the growth substrate.
Particularly preferably, the semiconductor layer is based on the same semiconductor compound material as the epitaxial semiconductor layer sequence to be grown on the growth substrate or consists of the same semiconductor compound material as the epitaxial semiconductor layer sequence to be grown on the growth substrate.
The buffer layer is based on a two-dimensional layered material or consists of a two-dimensional layered material. Particularly, two-dimensional layered materials comprises a plurality of monolayers of covalently bound elements, said monolayers of covalently bound elements are stacked above each other and bound to each other by weak Van der Waals forces.
According to a preferred embodiment, the growth substrate for the epitaxial growth of an epitaxial semiconductor layer sequence based on a semiconductor compound material, comprises a substrate, and a buffer layer sequence, said buffer layer sequence comprises at least one semiconductor layer based on the semiconductor compound material of the epitaxial semiconductor layer sequence to be grown on the growth substrate and at least one buffer layer based on a two-dimensional layered material.
According to a further embodiment of the growth substrate, the buffer layer is arranged in direct contact with the substrate. In particular, the buffer layer is bound to the substrate by weak Van der Waals forces.
According to a further embodiment of the growth substrate, the semiconductor layer forms a main surface of the growth substrate, said main surface being configured for the epitaxial growth of the epitaxial semiconductor layer sequence.
According to a further embodiment, the growth substrate comprises a plurality of buffer layers and a plurality of semiconductor layers or consists of a plurality of buffer layers and a plurality of semiconductor layers. Particularly preferably, the buffer layers and the semiconductor layers are arranged alternatingly. Preferably, each buffer layer is in direct contact with a semiconductor layer and vice versa.
In the following features and properties of the buffer layer and of the semiconductor layer are described in singular for the sake of simplicity. However, features and properties described in connection with one buffer layer or one semiconductor layer can be embodied for some or all buffer layers and/or semiconductor layers of the buffer layer sequence.
According to a further embodiment, the growth substrate is configured for the epitaxial growth of an epitaxial semiconductor layer sequence based on a nitride semiconductor compound material or consisting of a nitride semiconductor compound material. Nitride compound semiconductor materials are compound semiconductor materials containing nitrogen, such as the materials from the system InxAlyGa1-x-yN with 0≤x≤1, 0≤y≤1 and x+y≤1.
According to a further embodiment of the growth substrate, the buffer layer sequence comprises a plurality of semiconductor layers based on a nitride semiconductor compound material or formed from a nitride semiconductor compound material. Furthermore, the buffer layer sequence comprises a plurality of buffer layers. The semiconductor layers and the buffer layers comprised by the buffer layer sequence are arranged alternatingly. Such a growth substrate is particularly configured for the epitaxial growth of an epitaxial semiconductor layer sequence based on a nitride semiconductor compound material.
If the epitaxial semiconductor layer sequence to be grown on the growth substrate is based on a nitride semiconductor compound material or consists of a nitride semiconductor compound material, the semiconductor layer of the buffer layer sequence is preferably also based on a nitride semiconductor compound material or consists of a nitride semiconductor compound material.
Particularly preferably, an aluminium content of the semiconductor layers of the buffer layer sequence increases from the substrate, in particular in a linear or stepwise manner, to the main surface of the growth substrate intended for epitaxial growth in this case. For example, the aluminium content increases continuously within the semiconductor layers from the substrate to the main surface. In other words, the difference in the aluminium content of the semiconductor layers increases from the substrate to the main surface by the same amount.
Preferably, the semiconductor layer being furthest away from the substrate has an aluminium content which differs from the aluminium content of the epitaxial semiconductor layer sequence to be grown on the growth substrate by not less than 10%, preferably, by not less than 5%. Preferably, the semiconductor layer being furthest away from the substrate forms the main surface of the growth substrate, said main surface being intended for epitaxial growth.
Such a growth substrate is particularly configured for the epitaxial growth of an epitaxial semiconductor layer sequence based on a nitride compound semiconductor material having an high aluminium content. For example, the material of the epitaxial semiconductor layer sequence to be grown on the substrate has a ternary composition AlGaN.
In the case that the epitaxial semiconductor layer sequence to be grown on the growth substrate is based on a nitride semiconductor compound material or consists of a nitride semiconductor compound material, it is also possible that an indium content of the semiconductor layers of the buffer layer sequence increases from the substrate, in particular in a linear or stepwise manner, to the main surface of the growth substrate intended for epitaxial growth in this case. For example, the indium content increases continuously within the semiconductor layers from the substrate to the main surface. In other words, the difference in the indium content of the semiconductor layers increases from the substrate to the main surface by the same amount. Preferably, the semiconductor layer being furthest away from the substrate has an indium content which differs from the indium content of the epitaxial semiconductor layer sequence to be grown on the growth substrate by not less than 10%, preferably, by not less than 5%. Preferably, the semiconductor layer being furthest away from the substrate forms the main surface of the growth substrate, said main surface being intended for epitaxial growth.
Such a growth substrate is particularly configured for the epitaxial growth of an epitaxial semiconductor layer sequence based on a nitride compound semiconductor material having an high indium content. For example, the material of the epitaxial semiconductor layer sequence to be grown on the substrate has a ternary composition InGaN.
For example, the buffer layer comprises at least one of the following two-dimension layered materials or consists of at least one of the two-dimension layered materials: graphene, boron nitride (BN), MoS2, WSe2, fluorographene.
According to a further embodiment of the growth substrate the semiconductor layer of the buffer layer sequence is epitaxially grown. Particularly preferably, the semiconductor layer of the buffer layer sequence is epitaxially grown by MOVPE(short for: “metal organic vapor phase epitaxy”).
Particularly preferably, the semiconductor layer and the buffer layer of the buffer layer sequence are deposited by the same method. In such a way it is possible to deposit all layers of the buffer layer sequence without changing a deposition chamber. Preferably, the buffer layer is epitaxially grown, for example, by MOVPE.
Furthermore, the buffer layer might be deposited by the help of PVD (short for: “physical vapour deposition”), CVD (short for: “chemical vapour deposition”), MBE (short for: “molecular beam epitaxy”) or ALD (short for: “atomic layer deposition”).
According to a further embodiment of the growth substrate, the semiconductor layer has a thickness between 1 Nanometer and 2 Micrometer, limits inclusive. In particular, the semiconductor layer has a thickness between 1 Nanometer and 1 Micrometer, limits inclusive.
According to a further embodiment of the growth substrate, the buffer layer has a thickness between 1.3 Nanometer and 500 Nanometer, limits inclusive. In particular, the buffer layer has a thickness between 1.3 Nanometer and 100 Nanometer, limits inclusive. For example, a lower limit of the buffer layer is given by the thickness of a monolayer of the respective two-dimensional material of the buffer layer.
According to a further embodiment of the growth substrate, the semiconductor layer of the buffer layer sequence is at least partially strain relaxed. This is particularly possible with advantage, since the buffer layer is based on a two-dimensional layered material. Two-dimensional layered materials allow the semiconductor layer to slide on the buffer layer.
According to a further embodiment of the growth substrate, the substrate comprises at least one of the following materials or consists of at least one of the following materials: sapphire, (In,Al,Ga)N, silicon, silicon carbide or a non-crystalline substrate such as glass.
The growth substrate described herein is configured for the epitaxial growth of an epitaxial semiconductor layer sequence. Particularly preferably, the epitaxial semiconductor layer sequence is part of an optoelectronic semiconductor body. In the following, a method for manufacturing the optoelectronic semiconductor body is described. Features, embodiments and developments of the growth substrate can also be embodied by the method, the semiconductor body and vice versa.
According to an embodiment of the method for manufacturing an optoelectronic semiconductor body, a growth substrate is provided.
According to a further embodiment of the method, an epitaxial semiconductor layer sequence based on a semiconductor compound material is epitaxially grown on a main surface of the growth substrate. The epitaxial semiconductor layer sequence comprises an active zone being configured for generating and/or detecting electromagnetic radiation. In particular, the epitaxial semiconductor layer sequence is bound to the growth substrate by weak Van der Waals forces.
According to a preferred embodiment, the method for manufacturing an optoelectronic semiconductor body comprises the following steps:
Preferably, the method steps are performed in the given order.
According to a further embodiment of the method, the epitaxial semiconductor layer sequence is removed from the growth substrate by exfoliating. After exfoliation, the growth substrate can be reused. For example, the exfoliating can be carried out with the help of a chuck. In particular, it is not necessary to use a complex method for removing the epitaxial semiconductor layer sequence from the growth substrate such as, for example, a laser lift-off method, since the layers of the buffer layer sequence are connected to each other by weak Van der Waals forces. It is possible that a part of the buffer layer sequence still remains at the epitaxial semiconductor layer sequence after removal of the growth substrate.
According to a further embodiment of the method, the epitaxial semiconductor layer sequence is based on a nitride semiconductor compound material with the chemical formula InxAlyGa1−x−yN with 0≤x≤1, 0≤y≤1 and x+y≤1. In that case the active zone can be configured to emit and/or detect electromagnetic radiation with a wavelength between 200 Nanometer and 1770 Nanometer, limits inclusive. Particularly, electromagnetic radiation with wavelength in the UV region is generated and/or detected by active regions based on AlN, while electromagnetic radiation with wavelength in the IR region is generated and/or detected by active regions based on InN. Particularly, electromagnetic radiation with wavelength in the visible region is generated and/or detected by active regions based on a nitride semiconductor compound material comprising In, Al and Ga.
According to a further embodiment of the method during providing the growth substrate a substrate is provided. On the substrate a buffer layer sequence is deposited. Preferably, the deposition of the buffer layer sequence takes place in the same deposition chamber as the epitaxial growth of the epitaxial semiconductor layer sequence. At this embodiment of the method, the layers of the buffer layer sequence, namely the semiconductor layer and the buffer layer are grown by the same method. Preferably, the layers of the buffer layer sequence are grown by MOVPE. Further, it is also possible that the layers of the buffer layer sequence and the epitaxial semiconductor layer sequence are grown by different methods. If this is the case, the layers of the buffer layer sequence and the epitaxial semiconductor layer sequence are deposited in different deposition chambers. In particular, also the semiconductor layer of the buffer layer sequence and the buffer layer of the buffer layer sequence are deposited by different methods and in different deposition chambers, if this is the case.
According to a further embodiment of the method, a substrate is provided. On the substrate a buffer layer sequence is deposited. Preferably, depositing a plurality of buffer layers of the buffer layer sequence takes place in a different deposition chambers. In particular, the buffer layer of the buffer layer sequence and the semiconductor layer of the buffer layer sequence are deposited in different deposition chambers.
According to a further embodiment of the method, the epitaxial semiconductor layer sequence is arranged on a carrier. The carrier is configured to mechanically stabilize the epitaxial semiconductor layer sequence. The carrier can be fixed to the epitaxial semiconductor layer sequence before or after removal from the growth substrate. Preferably, the carrier is fixed to the epitaxial semiconductor layer sequence before removal of the growth substrate. The carrier can be embodied as a carrier wafer.
Particularly preferably, the growth substrate disclosed herein enables an improved epitaxial growth of a epitaxial semiconductor layer sequence, in particular comprising hetero structures.
The semiconductor body, which is produced by the method described herein, might be configured to be part of a light-emitting diode, a laser diode or a detector for electromagnetic radiation such as a photodiode.
In general, no growth substrates for the growth of epitaxial semiconductor layer sequences based on compound semiconductor materials with the same lattice constant as the lattice constant of the epitaxial semiconductor layer sequence are available. Commonly, growth substrates are used having a lattice constant different from the lattice constant of the epitaxial semiconductor layer sequence to be grown. This leads to a mismatch in the lattice parameters lowering crystal quality of the epitaxial semiconductor layer sequence.
Inter alia, the present growth substrate is based on the idea that with the help of the semiconductor layers of the buffer layer sequence, the lattice constant of the semiconductor material comprised by the buffer layer sequence can be adapted stepwise from the substrate to a main surface of the growth substrate. In such a way, the lattice mismatch between the material of the epitaxial semiconductor layer sequence to be grown and the growth substrate can be reduced. This leads to an epitaxial semiconductor layer sequence having improved crystal quality.
Further, strain relaxation within the buffer layer sequence, for example due to the different material composition of the semiconductor layers, preferably takes place by sliding of the semiconductor layers on the buffer layers, which is enabled by the nature of the two-dimensional layered materials of the buffer layers, which are bound to the respective adjacent semiconductor layers only by weak Van der Waals forces.
Particularly preferably, it is possible to provide a growth substrate for improved epitaxial growth of an epitaxial semiconductor layer sequence based on a nitride semiconductor compound material having a high indium content or a high aluminium content. Particularly, growth substrates for the growth of such epitaxial semiconductor layer sequences comprises buffer layer sequences, wherein the indium content or the aluminium content of the semiconductor layers of the buffer layer sequence increases stepwise, starting from the substrate to the main surface of the growth substrate.
Further advantageous embodiments and developments of the growth substrate and the method for manufacturing an optoelectronic semiconductor body result from the exemplary embodiment described below in connection with the Figures.
Equal or similar elements as well as elements of equal function are designated with the same reference signs in the Figures. The Figures and the proportions of the elements shown in the Figures are not regarded as being shown to scale. Rather, single elements, in particular layers, can be shown exaggerated in magnitude for the sake of better presentation and/or better understanding.
The growth substrate 1 according to the exemplary embodiment of
Furthermore, the growth substrate 1 according to the exemplary embodiment of
The buffer layer 31 is arranged in direct contact with a main surface 4 of the substrate 2. The buffer layer 31 comprises a two-dimensional layered material or consists of a two-dimensional layered material. For example, the buffer layer 31 comprises or consists of at least one of the following two-dimensional layered materials: graphene, boron nitride, MoS2, WSe2, fluorographene.
The semiconductor layer 32 of the buffer layer sequence 3 according to the exemplary embodiment of
Further, the growth substrate 1 of the exemplary embodiment of
The growth substrate 1 according to the exemplary embodiment of
Further, the growth substrate 1 according to the exemplary embodiment of
The buffer layer sequence 3 of the growth substrate 1 according to the exemplary embodiment of
Furthermore, the buffer layer sequence 3 comprises three semiconductor layers 32, 32′, 32″. Further, it is possible that the buffer layer sequence 3 comprises more or less than three semiconductor layers 32, 32′, 32″. Preferably, the number of the buffer layers 31 of the buffer layer sequence 3 and the number of the semiconductor layers 32 of the buffer layer sequence 3 are equal. The semiconductor layers 32 and the buffer layers 31 are arranged alternatingly with each other.
Further, one buffer layer 31 is arranged directly adjacent to the substrate 2, while a main surface 6 of the growth substrate 1 intended for epitaxial growth of an epitaxial semiconductor layer sequence 5 is formed by a semiconductor layer 32″.
Each of the semiconductor layers 32, 32′, 32″ of the buffer layer sequence 3 comprises or consists of a nitride compound semiconductor material. At present, the semiconductor layers 32, 32′, 32″ of the buffer layer sequence 3 comprise or consist of InGaN. In particular, the indium content of the semiconductor layers 32, 32′, 32″ is increasing with the distance to the substrate 2. In other words, the semiconductor layer 32 closest to the substrate 2 has the lowest indium content, while the semiconductor layer 32″ arranged at a largest distance from the substrate 2 has the highest indium content.
The semiconductor layer 32 closest to the substrate 2 has a material composition InxGa1-xN, while the semiconductor layer 32″ having the largest distance to the substrate 1 has a material composition of InzGa1-zN. The semiconductor layer 32′ in between has a material composition of InyGa1-yN. Furthermore, the relation is x<y<z valid.
Alternatively, the semiconductor layers 32, 32′, 32″ of the buffer layer sequence 3 comprise or consist of AlGaN. In particular, the aluminium content of the semiconductor layers 32, 32′, 32″ is increasing with the distance to the substrate 2. In other words, the semiconductor layer 32 closest to the substrate 2 has the lowest aluminium content, while the semiconductor layer 32″ arranged at the largest distance to the substrate 2 has the highest aluminium content.
The semiconductor layer 32 closest to the substrate 2 has a material composition AlxGa1-xN, while the semiconductor layer 32″ having the largest distance to the substrate 2 has a material composition of AlzGa1-zN. The semiconductor layer 32′ in between has a material composition of AlyGa1-yN. Furthermore, the relation is x<y<z valid. It is also possible that z<y<x is valid.
In a first step of the method of the exemplary embodiment of
The growth substrate 1 comprises a buffer layer sequence 3 with a plurality of buffer layers 31 and a plurality of semiconductor layers 32. The buffer layers 31 and the semiconductor layers 32 are arranged alternatingly. The semiconductor layers 32 are formed from a semiconductor compound material, while the buffer layers 31 are formed from a two-dimensional layered material.
The growth substrate 1 has a main surface 6 intended for the growth of an epitaxial semiconductor layer sequence 5. The main surface 6 intended for the growth of the epitaxial semiconductor layer sequence 5 is formed from the material of one of the semiconductor layers 32. A lattice constant of the material of the main surface 6 intended for the growth of the epitaxial semiconductor layer sequence 5 is similar to a lattice constant of the epitaxial semiconductor layer sequence 5 to be grown on the main surface 6 of the growth substrate 1.
After providing the growth substrate 1 in the deposition chamber 7, an epitaxial semiconductor layer sequence 5 based on a compound semiconductor material is epitaxially grown on the main surface 6 of the growth substrate 1 (
For example, the buffer layer sequence 3 is deposited in the deposition chamber 7 prior to the growth of the epitaxial semiconductor layer sequence 5 without leaving the deposition chamber 7. In this case, the layers of the buffer layer sequence 3, namely the semiconductor layers 32 and the buffer layers 31 are grown by the same method as the epitaxial semiconductor layer sequence 5, preferably by MOVPE.
Alternatively, it is also possible to deposit the layers of the buffer layer sequence 3 and the epitaxial semiconductor layer sequence 5 by different deposition methods. For example, the layers of the buffer layer sequence 3 are deposited by PVD, CVD, ALD and/or MBE, while the epitaxial semiconductor layer sequence 5 is deposited by MOVPE.
The epitaxial semiconductor layer sequence 5 comprises an active zone 8, which is configured to emit or to detect electromagnetic radiation during operation. The active zone 8 comprises for example a pn-transition, a double hetero structure, a single quantum structure or a multi quantum structure for the generation and/or detection of the electromagnetic radiation. Here, the term “quantum structure” means quantum wells, quantum wires as wells as quantum dots.
At present, the epitaxial semiconductor layer sequence 5 grown on the main surface 6 of the growth substrate 1 is based on a nitride compound semiconductor material. Further, the semiconductor layers 32 of the buffer layer sequence 3 are also based on a nitride compound semiconductor material.
In a next step, which is schematically shown in
During the exfoliation process it is possible that a part of the buffer layer sequence 3 still remains at the epitaxial semiconductor layer sequence 5. In other words, it is possible that a separation due to the applied force F by the chuck 9 takes place within the buffer layer sequence 3.
As shown schematically in
Before or after the exfoliation it is possible that the epitaxial semiconductor layer sequence 5 is arranged on a carrier 10 (
The features and exemplary embodiments described in connection with the Figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the Figures may alternatively or additionally have further features according to the description in the general part.
The invention is not limited to the description of the embodiments. Rather, the invention comprises each new feature as well as each combination of features, particularly each combination of features of the claims, even if the feature or the combination of features itself is not explicitly given in the claims or embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 202 708.3 | Mar 2021 | DE | national |
This patent application is a national phase filing under section 371 of PCT/EP2022/055282, filed Mar. 2, 2022, which claims the priority of German patent application 10 2021 202 708.3, filed Mar. 19, 2021, each of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/055282 | 3/2/2022 | WO |
