CN-121986573-A - Substrate for epitaxial growth, method for manufacturing optical semiconductor element, and optical semiconductor element

Abstract

Provided is a substrate for epitaxial growth having a buffer laminate, wherein cracking does not occur even when a support substrate is bonded or an initial growth substrate is removed. An epitaxial growth substrate comprises an initial growth substrate, an etching stop layer on the initial growth substrate, and a buffer laminate on the etching stop layer, wherein the buffer laminate comprises N buffer layers having different lattice constants from each other, and a dummy substrate layer having a thickness of 300nm or more on the N buffer layers, and the substrate for epitaxial growth has 3 or more buffer layers containing misfit dislocation on the initial growth substrate side of the buffer layers, wherein the lattice constant of the initial growth substrate is a g , the lattice constant of the dummy substrate layer is a p , the degree of mismatching X p·g of the dummy substrate layer with respect to the initial growth substrate is 0.7% or more, and the N is a natural number of 3 or more.

Inventors

• Yotaro

Assignees

• 同和电子科技有限公司

Dates

Publication Date

20260505

Application Date

20241023

Priority Date

20231031

Claims (20)

1. 1. An epitaxial growth substrate, comprising: a substrate for initial growth, An etching stop layer on the substrate for initial growth, and A buffer stack on the etch stop layer, The buffer laminate comprises N buffer layers having different lattice constants from each other, and a dummy substrate layer having a thickness of 300nm or more on the N buffer layers, When the lattice constant of the substrate for initial growth is a g and the lattice constant of the dummy substrate layer is a p , the degree of mismatch X p·g of the dummy substrate layer with respect to the substrate for initial growth is 0.7% or more, The N is a natural number above 3, The substrate for epitaxial growth has 3 or more buffer layers containing misfit dislocation on the substrate side for initial growth of the buffer layers.
2. 2. The substrate for epitaxial growth according to claim 1, wherein, When the lattice constant in the vertical direction calculated from the reciprocal space map of the dummy substrate layer is q z and the lattice constant in the horizontal direction is q x , the following expression (2) is satisfied: -0.0002≤q z -q x ≤0.0011 (2)。
3. 3. The substrate for epitaxial growth according to claim 1, wherein a lattice-like pattern is observed when a plan view of the surface of the dummy substrate layer is photographed by a metal microscope.
4. 4. The substrate for epitaxial growth according to claim 1, wherein, When the lattice constant of the n-th buffer layer from the buffer layer located closest to the substrate for initial growth is a n and the lattice constant of the n+1th buffer layer is a n+1 , the following formula (1) is satisfied: a n ＜a n+1 (1), In the above formula, n is 1 to N-1, The lattice constant a 1 at n of 1 is greater than the a g , The lattice constant a N for N +1 is smaller than the a p , The degree of mismatch with respect to the layer adjacent to the substrate for initial growth among the N buffer layers is set to be equal to or less than the value obtained by dividing the degree of mismatch X p·g by N.
5. 5. The epitaxial growth substrate according to claim 1, wherein the buffer layers are each composed of a single layer or a plurality of buffer constituent layers, and the thickness of each buffer layer is 150nm or more.
6. 6. The substrate for epitaxial growth of claim 4, wherein, At least one buffer layer is formed of a plurality of buffer formation layers, The buffer constituent layer A located on the side of the dummy substrate layer in the buffer layer is thicker than the buffer constituent layer B located on the side of the dummy substrate layer in the buffer layer, Here, the lattice constant of the buffer layer in formula (1) uses the lattice constant of the buffer constituent layer a.
7. 7. The epitaxial growth substrate according to claim 6, wherein the thickness of the buffer composition layer a is 100nm or more, and the thickness of the buffer composition layer B is half or less of the thickness of the buffer composition layer a.
8. 8. The substrate for epitaxial growth according to claim 1, wherein the substrate for initial growth is an InP substrate and the etching stopper layer is an InGaAs layer.
9. 9. The substrate for epitaxial growth according to claim 1, wherein the substrate for initial growth is an InP substrate, the buffer stack is a stack of a plurality of InAsP layers, and the buffer stack further has an InP window layer in contact with the etch stop layer.
10. 10. A method of manufacturing an optical semiconductor element, comprising: a step of forming a semiconductor laminate including an active layer on the dummy substrate layer of the substrate for epitaxial growth according to any one of claims 1 to 9; a step of bonding a support substrate to the semiconductor laminate via a reflective layer, and And removing the initial growth substrate of the epitaxial growth substrate.
11. 11. The method for manufacturing an optical semiconductor element according to claim 10, wherein a SORI value of the surface side of the semiconductor laminate on the analog substrate layer obtained by the step of forming the semiconductor laminate is less than 30 μm.
12. 12. An optical semiconductor device comprising, in order, a support substrate, a reflective layer, a semiconductor laminate including an active layer, and a buffer laminate, The buffer laminate comprises, in order, a simulation substrate layer having a thickness of 300nm or more, N buffer layers, and a window layer located on the light extraction side, When the lattice constants of the dummy substrate layer and the window layer are a p and a t , respectively, the degree of mismatch X p·t of the dummy substrate layer with respect to the window layer is 0.7% or more, The N is a natural number above 3, The optical semiconductor element has more than 3 buffer layers containing misfit dislocation on the window layer side of the buffer layers.
13. 13. The optical semiconductor element according to claim 12, wherein, When the lattice constant of the n-th buffer layer from the buffer layer located closest to the window layer is a n and the lattice constant of the n+1th buffer layer is a n+1 , the following formula (1) is satisfied: a n ＜a n+1 (1), In the above formula, n is 1 to N-1, The lattice constant a 1 at n of 1 is greater than the a t , The lattice constant a N for N +1 is smaller than the a p , The degree of mismatch with respect to the adjacent layer on the window layer side in each of the N buffer layers is set to be equal to or less than the value obtained by dividing the degree of mismatch X p·t by N.
14. 14. The optical-semiconductor element according to claim 12, wherein a refractive index gradually decreases from the dummy substrate layer toward a window layer.
15. 15. The optical semiconductor element of claim 12 wherein the window layer is InP, the buffer stack is a stack of a plurality of InAsP layers, and the analog substrate layer is an InAsP layer.
16. 16. The optical semiconductor element according to claim 12, wherein a light emission center wavelength of the active layer in the semiconductor laminate is 2000 to 3000nm.
17. 17. The optical semiconductor element according to claim 12, wherein, The active layer has a quantum well structure, and when the lattice constant of the well layer is set to a w , The degree of mismatch X w·p of the well layer relative to the analog substrate layer is 0.1% or more and less than 1.2%.
18. 18. The optical semiconductor element according to claim 17, wherein, among lattice constants of the semiconductor stack and buffer stack, a lattice constant a w of a well layer of the active layer is largest.
19. 19. The optical semiconductor element according to claim 12, wherein the buffer layers are each composed of a single layer or a plurality of buffer constituent layers, and the thickness of each buffer layer is 150nm or more.
20. 20. The optical semiconductor element according to claim 13, wherein, At least one buffer layer is formed of a plurality of buffer formation layers, The buffer constituent layer A located on the side of the dummy substrate layer in the buffer layer is thicker than the buffer constituent layer B located on the side of the dummy substrate layer in the buffer layer, Here, the lattice constant of the buffer layer in formula (1) uses the lattice constant of the buffer constituent layer a.

Description

Substrate for epitaxial growth, method for manufacturing optical semiconductor element, and optical semiconductor element Technical Field The invention relates to a substrate for epitaxial growth, a method for manufacturing an optical semiconductor element, and an optical semiconductor element. Background An optical semiconductor device is often manufactured through a process of epitaxially growing a semiconductor laminate including an active layer on an initial growth substrate. Here, the ratio Δa/a of the difference (Δa) between the lattice constants of the substrate for initial growth and the epitaxial layer formed by epitaxial growth to the lattice constant a of the substrate for initial growth is referred to as lattice mismatch degree. If the lattice mismatch degree is small, epitaxial growth can be performed without generating defects, and if the film thickness of the epitaxial layer is sufficiently thin, growth can be performed by the lattice strain of the epitaxial layer while maintaining the continuity of the lattice at the interface (co-growth). The upper limit of the film thickness that can grow cohesively even if the lattice mismatch degree is large is called a critical film thickness. The step of growing a lattice-matched layer generally means epitaxial growth in which the lattice mismatch degree is within ±0.1% and is close to zero. In the case of growing a layer having a lattice mismatch, for example, epitaxial growth is generally performed within a range where layers having a lattice mismatch degree of ±0.3% or less are grown together. On the other hand, in the case of epitaxially growing a layer having a lattice mismatch degree of more than 0.3% with respect to the lattice constant of the substrate for initial growth on the substrate for initial growth, a method of growing a layer on the substrate for initial growth via a buffer layer is known. For example, patent document 1 proposes providing a buffer layer formed between a substrate and a light absorbing layer, the lattice constant of which gradually changes from that of the substrate to that of the absorbing layer. Specifically, each layer of the buffer layer is formed to have a critical film thickness or less to suppress the occurrence of crystal defects. In patent document 2, in order to alleviate lattice mismatch between InP and GaInAs absorption layers, it is proposed to form GaInAs absorption layers having a lattice mismatch ratio of 0.5% or more on buffers in which strained superlattice layers of a combination of InAs XP1-X/InAsYP1-Y are interposed in multiple stages. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2001-102620 Patent document 2 Japanese patent laid-open No. 6-188447 Disclosure of Invention Problems to be solved by the invention The present inventors have developed a technique of, in the past, using an InP substrate for an initial growth substrate, without removing a transparent initial growth substrate, directly using a thick InP initial growth substrate is preferable for improving light extraction, and specifically removing an InP initial growth substrate and bonding a support substrate in a wavelength range of 1000nm to 1700nm (for example, 1300 nm), thereby improving light emission efficiency. Further, whether or not such a technique can be applied to an optical semiconductor element having a wavelength region exceeding 1700nm and an optical semiconductor element having another wavelength region has been studied. In the case of an optical semiconductor device having a wavelength region exceeding 1700nm, for example, an optical semiconductor device having a wavelength region of 2000 to 3000nm, since the substrate for initial growth having a lattice constant close to that of the semiconductor laminate including the active layer having a desired wavelength cannot be selected, a layer having a large lattice mismatch degree with respect to the substrate for initial growth is epitaxially grown. In the method of growing a layer having a large lattice mismatch degree on a substrate for initial growth via a buffer layer, the strained superlattice buffer laminate and the composition tilt buffer described in patent documents 1 and 2 are formed while suppressing the occurrence of crystal defects (dislocations), and therefore, warpage occurs in the substrate due to lattice mismatch with the substrate for initial growth, or large stress is accumulated therein even when the substrate is thinned and no warpage occurs. If such internal stress is accumulated, the balance of the internal stress may change sharply when the substrate for initial growth is removed at the time of bonding the support substrate by the above technique, and thus cracks may occur. The present invention provides an epitaxial growth substrate having a buffer laminate, which does not cause cracking even when a support substrate is bonded or an initial growth substrate is removed, and a method for manufacturing an optical