An extended wavelength InGaAs detector structure and method of manufacture thereof

Abstract

This invention discloses an extended wavelength InGaAs detector structure and its fabrication method. The detector structure, from bottom to top, consists of a substrate, a pseudo-substrate, an absorption layer lattice-matched to the pseudo-substrate, and a cap layer. The fabrication method involves preparing a pseudo-substrate with a variable composition of high-In-content InAlAs or high-As-content InAsP via molecular beam epitaxy, and improving the material quality through chemical mechanical polishing (CMP) to complete the pseudo-substrate preparation. The surface after CMP is treated with wet etching. An extended wavelength InGaAs short-wave infrared detector is grown based on the CMP-polished InAlAs or InAsP epitaxial material. This invention can effectively reduce surface roughness, suppress the propagation of penetrating dislocations, and improve the photoelectric properties of the material.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic devices, and more specifically to an extended wavelength InGaAs detector structure and its manufacturing method. Background Technology

[0002] Extended-wavelength InGaAs detectors play a crucial role in aerospace remote sensing. Currently, InGaAs materials with higher In content are typically used for epitaxial growth of extended-wavelength InGaAs detector materials. However, this inevitably generates a large number of mismatched dislocations, resulting in higher defect-assisted tunneling dark currents. To achieve high signal-to-noise ratio short-wavelength infrared detection, it is essential to reduce the device's dark current density. Since there is no substrate with a lattice match to extended-wavelength InGaAs, InP substrates with similar lattice constants are commonly used. Structural optimization of the epitaxial buffer layer has, to some extent, effectively suppressed dislocation generation and climb. However, although numerous studies have reported on dislocation defect suppression in mismatched extended-wavelength InGaAs materials, the defect density in mismatched extended-wavelength InGaAs materials remains significantly higher than that in lattice-matched InP / In. 0.53 Ga 0.47 As detectors. Therefore, there are technical bottlenecks in achieving extended wavelength InGaAs detectors with extremely low defects and extremely low dark current on existing mature mismatched substrates, which limits the widespread application of extended wavelength InGaAs detectors.

[0003] Due to the release of compressive strain stress, InGaAs materials with lattice mismatch naturally develop a rough, textured surface with undulations reaching hundreds of nm and a roughness approaching 10 nm. These surface morphological undulations, such as cross shadows and mound-like structures, increase material inhomogeneity, thereby amplifying focal plane imaging inhomogeneity. Uneven morphology at heterojunction interfaces increases pn junction interface scattering, generating recombination dark currents. The rough surface also affects the interfacial compactness between the silicon nitride dielectric film and the semiconductor material, and significantly impacts the zinc diffusion process. Therefore, effectively controlling and reducing the surface roughness of lattice mismatch InGaAs detector epitaxial materials is a prerequisite for achieving high-performance, high-reliability lattice mismatch epitaxial devices. Summary of the Invention

[0004] The purpose of this invention is to provide an extended wavelength InGaAs detector structure and its manufacturing method, which solves the problems of quality degradation and dislocation defects in lattice-mismatched compressive strain InGaAs materials in the prior art. It also solves the problems of increased focal plane imaging non-uniformity and increased pn junction interface scattering generating recombination dark current in extended wavelength InGaAs materials due to the release process of compressive strain stress, which naturally forms a rough surface with undulations of hundreds of nm and a roughness of nearly 10 nm. This provides material support for the development of higher performance extended wavelength InGaAs focal plane detectors.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An InGaAs detector structure with extended wavelength, which includes a substrate, a pseudosubstrate, an absorption layer, and a cap layer from bottom to top; among them, the substrate is made of InP material, and the doping type is N-type or P-type doping; the pseudosubstrate is made of a material with a graded composition of In x Al 1-x As or InAs y P 1-y and the absorption layer is lattice-matched with the pseudosubstrate.

[0007] When the pseudosubstrate is a material with a graded composition of In x Al 1-x As, the composition x of In linearly varies from 0.52 to z, where 0.52 < z < 1; when the pseudosubstrate is a material with a graded composition of InAs y P 1-y the composition y of As linearly varies from 0 to k, where 0 < k < 1.

[0008] The polishing treatment of the pseudosubstrate is chemical mechanical polishing treatment.

[0009] The material of the absorption layer is InGaAs.

[0010] The material of the cap layer is InAlAs.

[0011] [[ID=3​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​1-x As or InAs y P 1-y The roughness and flatness of the material; then, the polished In is etched by wet etching x Al 1-x As or InAs y P 1-y The surface of the material is treated to remove the surface damage and contamination caused by chemical mechanical polishing.

[0017] On the InP substrate, a 10-μm compositionally graded In x Al 1-x As or InAs y P 1-y Pseudosubstrate of the material; when growing In x Al 1-x As material, the composition x of In linearly changes from 0.52 to z, 0.52 < z < 1; when growing InAs y P 1-y material, the composition y of As linearly changes from 0 to k, 0 < k < 1;

[0018] The thickness of the polished pseudosubstrate is 4 μm.

[0019] Step three is to grow an InGaAs absorption layer lattice-matched to the pseudosubstrate on the treated pseudosubstrate, with a growth thickness of 3 μm.

[0020] The growth thickness of the InAlAs cap layer is 1 μm.

[0021] In view of the above technical features, the present invention has the following beneficial effects: 1. The present invention adopts the technical route of forming a pseudosubstrate after "epitaxy + polishing" and then secondary epitaxy, and introduces the preparation of extended wavelength InGaAs detector materials, which can effectively overcome the technical difficulties of epitaxial growth of extended wavelength InGaAs detector materials in a mismatch system. Atomic force microscope tests show that after chemical mechanical polishing, the surface roughness of the material is reduced from greater than 2.5 nm to 0.752 nm, solving the problem of difficult to balance the surface flatness and crystal quality of the material, and can effectively reduce the surface roughness and non-uniformity of the material; 2. The polished pseudosubstrate can effectively reduce the propagation of threading dislocations to the epitaxial layer, thereby reducing dislocations, improving the material uniformity, and further enhancing the detector performance; 3. The present invention realizes the preparation of extremely low-defect lattice-matched extended wavelength InGaAs detector materials and devices, significantly reduces the dark current and noise of indium gallium arsenide detectors, improves the detectivity and uniformity, and promotes the performance development of extended wavelength infrared focal plane detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the present invention;

[0023] Figure 2 is the flowchart of the manufacturing method of the present invention;

[0024] Figure 3 is the atomic force microscope test chart of the pseudo-substrate structure of the present invention before chemical mechanical polishing;

[0025] Figure 4 is the atomic force microscope test chart of the pseudo-substrate structure of the present invention after chemical mechanical polishing;

[0026] In the figure: 1 - substrate; 2 - pseudo-substrate; 3 - absorption layer; 4 - cap layer. Specific embodiments

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these drawings and embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that some components well known to those skilled in the art but not relevant to the main content of this creation will be omitted in the drawings or descriptions. In addition, for the convenience of expression, some components in the drawings will be omitted, enlarged or reduced, but do not represent the size or all structures of the actual product.

[0028] An InGaAs detector structure with an extended wavelength, as Figure 1 shown, it includes a substrate 1, a pseudo-substrate 2, an absorption layer 3 and a cap layer 4 from bottom to top; among them, the substrate 1 is made of InP material, and the doping type is N-type or P-type doping; the pseudo-substrate 2 is made of a material with a graded composition of In x Al 1-x As or InAs y P 1-y after polishing; the absorption layer 3 is lattice-matched with the pseudo-substrate 2.

[0029] When the pseudo-substrate 2 is a material with a graded composition of In x Al 1-x As, the component x of In linearly varies from 0.52 to z, 0.52 < z < 1; when the pseudo-substrate 2 is a material with a graded composition of InAs y P 1-y material, the component y of As linearly varies from 0 to k, 0 < k < 1.

[0030] Furthermore, the polishing treatment of the pseudo-substrate 2 is chemical mechanical polishing treatment, as Figure 3 , Figure 4 compared, the surface roughness of the material before chemical mechanical polishing treatment is greater than 2.5 nm, and it is reduced to 0.752 nm after chemical mechanical polishing treatment, significantly reducing the surface roughness of the pseudo-substrate 2 material, thus solving the difficult problem of hard to balance the surface flatness and crystal quality of the material.

[0031] The material of the absorption layer 3 is InGaAs, which is lattice-matched with the pseudo-substrate 2.

[0032] The material of the cap layer 4 is InAlAs.

[0033] A method for manufacturing an InGaAs detector structure with extended wavelength as described above, the specific steps are as follows:

[0034] Step 1, grow multiple layers of In x Al 1-x As or InAs y P 1-y materials on the InP substrate 1 by molecular beam epitaxy;

[0035] Grow a pseudo-substrate 2 of In x Al 1-x As or InAs y P 1-y material with a component gradient of about 10 μm on the InP substrate 1 by molecular beam epitaxy; when growing In x Al 1-x As material, the component x of In linearly changes from 0.52 to z, 0.52 < z < 1; when growing InAs y P 1-y material, the component y of As linearly changes from 0 to k, 0 < k < 1;

[0036] Step 2, process the multiple layers of In x Al 1-x As or InAs y P 1-y materials to complete the preparation of the pseudo-substrate 2;

[0037] First, improve the roughness and flatness of the In x Al 1-x As or InAs y P 1-y material by chemical mechanical polishing; then use wet etching to treat the surface of the polished In x Al 1-x As or InAs y P 1-y material surface to remove the surface damage and contamination caused by chemical mechanical polishing.

[0038] The thickness of the polished pseudo-substrate 2 is 4 μm. [[ID=7l]]

[0039] Step 3, grow the InGaAs absorption layer 3 on the pseudo-substrate 2 by molecular beam epitaxy; the InGaAs absorption layer 3 is lattice-matched with the pseudo-substrate 2, and the growth thickness is 3 μm.

[0040] Step 4: An InAlAs cap layer 4 is grown on the absorption layer 3 using molecular beam epitaxy. The growth thickness of the InAlAs cap layer 4 is 1 μm.

[0041] Example 1, the specific steps are as follows:

[0042] In with compositional variation is grown on InP substrate 1 by molecular beam epitaxy. x Al 1-x As pseudo-substrate 2 structure. The In composition x linearly changes from 0.52 at the interface with substrate 1 to 0.75 at the surface, with the In composition-gradient layer thickness approximately 2 μm. 0.75 Al 0.25 The As thickness is approximately 7 μm, the total thickness of the gradient layer is 9 μm, the growth temperature is approximately 900℃, and the growth rate is approximately 0.6 μm / h.

[0043] Chemical mechanical polishing (CMP) was used to planarize the surface globally, uniformly reducing the total thickness of the InAlAs material in the pseudo-substrate 2 to approximately 3 μm, with a surface roughness of less than 1 nm.

[0044] To remove the mechanical damage layer (approximately tens of nanometers) caused by polishing, as well as any adhering abrasive contaminants, wet etching cleaning was performed. The etching solution had a volume ratio of H3PO4:H2O2:H2O = 3:1:50. Immersion was carried out at 22°C for 60 seconds, followed by nitrogen purging for 30 seconds. The sample was then transferred to a plasma cleaning system for ozone plasma treatment. Treatment was performed at 200 W RF power and 200 sccm oxygen flow rate for 5 minutes. This thoroughly decomposed and removed any organic contaminants that might have remained from polishing and wet cleaning.

[0045] On the treated pseudo-substrate 2 surface, a 2.5 μm thick In layer was grown using molecular beam epitaxy. 0.75 Ga 0.25 As absorption layer 3, with a doping concentration of 5×10⁻⁶. 16 cm -3 The growth temperature is approximately 600 ℃, and the growth rate is approximately 0.8 μm / h.

[0046] A 0.6 μm thick In layer was grown on absorber layer 3. 0.75 Al 0.25 As cap layer 4 is used to protect the surface of absorber layer 3 and complete the device structure, with a doping concentration of 3×10⁻⁶. 16 cm -3 The growth temperature is approximately 600 ℃, and the growth rate is approximately 0.8 μm / h.

[0047] Example 2, the specific steps are as follows:

[0048] Compositionally graded InAs are grown on InP substrates 1 with N-type or P-type doping concentrations. y P 1-y Pseudo-substrate 2 has an As composition y that linearly changes from 0 to 0.47 from bottom to top, with the thickness of the gradient layer being approximately 4 μm. (InAs) 0.47 P 0.53 The thickness is approximately 8 μm, the total thickness of the gradient layer is 12 μm, the growth temperature is approximately 500℃, and the growth rate is approximately 0.8 μm / h.

[0049] Chemical mechanical polishing was used to planarize the surface globally, reducing the material thickness uniformly from 12 μm to 4 μm, and controlling the surface roughness to below 1 nm.

[0050] After polishing, wet etching cleaning is performed. An etching solution with a volume ratio of H3PO4 : H2O2 : H2O = 3 : 1 : 50 is used. The solution is immersed at 22°C for 90 s, followed by rinsing with a 50% HF solution for 30 s to remove any natural oxide layer and some metallic contaminants that may be present on the surface.

[0051] A 2.5 μm thick In layer was grown on the treated pseudo-substrate 2 using molecular beam epitaxy. 0.75 Ga 0.25 As absorption layer 3, with a doping concentration of 5×10⁻⁶. 16 cm -3 The growth temperature is approximately 600℃, and the growth rate is approximately 0.8 μm / h.

[0052] A 0.6 μm thick In layer was grown on absorber layer 3. 0.75 Al 0.25 As cap layer 4 is used to protect the surface of absorber layer 3 and complete the device structure, with a doping concentration of 3×10⁻⁶. 16 cm -3 The growth temperature is approximately 600 ℃, and the growth rate is approximately 0.8 μm / h.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. An extended wavelength InGaAs detector structure, characterized in that: It comprises, from bottom to top, a substrate (1), a pseudo-substrate (2), an absorber layer (3), and a cap layer (4); wherein, the substrate (1) is an InP material, with N-type or P-type doping; the pseudo-substrate (2) is a polished material composed of a gradient In composition. x Al 1-x As or InAs y P 1-y The material composition; the absorber layer (3) is lattice matched with the pseudo-substrate (2).

2. The InGaAs detector structure as described in claim 1, characterized in that: When the pseudo-substrate (2) is a In x Al 1-x As material, the component x of In linearly changes from 0.52 to z, where 0.52 < z < 1; when the pseudo-substrate (2) is a InAs y P 1-y material, the component y of As linearly changes from 0 to k, where 0 < k < 1.

3. The InGaAs detector structure as described in claim 2, characterized in that: The polishing process for the pseudo-substrate (2) is chemical mechanical polishing.

4. The InGaAs detector structure as described in claim 1, characterized in that: The material of the absorption layer (3) is InGaAs.

5. The InGaAs detector structure as described in claim 1, characterized in that: The cap layer (4) is made of InAlAs.

6. A method for manufacturing an extended wavelength InGaAs detector structure as described in any one of claims 1-5, characterized in that: The specific steps are as follows: Step 1: Multilayer In atoms are grown on an InP substrate (1) using molecular beam epitaxy. x Al 1-x As or InAs y P 1-y Material; Step 2, for multi-layer In x Al 1-x As or InAs y P 1-y The materials are processed to complete the preparation of the pseudo-substrate (2); Step 3: An InGaAs absorption layer (3) is grown on the pseudo-substrate (2) using molecular beam epitaxy. Step 4: Use molecular beam epitaxy to grow an InAlAs cap layer (4) on the absorption layer (3).

7. The method for manufacturing the InGaAs detector structure as described in claim 6, characterized in that: The process of preparing the pseudo-substrate (2) in step two is as follows: first, chemical mechanical polishing is used to improve the In... x Al 1-x As or InAs y P 1-y The roughness and flatness of the material; then wet etching is used to refine the polished In. x Al 1-x As or InAs y P 1-y The material surface is treated to remove surface damage and contamination caused by chemical mechanical polishing.

8. The method for manufacturing the InGaAs detector structure as described in claim 7, characterized in that: On an InP substrate (1), a pseudo-substrate (2) of In x Al 1-x As or InAs y P material with a composition gradient of 10 μm is grown by molecular beam epitaxy; when growing In x Al 1-x As material, the composition x of In linearly changes from 0.52 to z, where 0.52 < z < 1; when growing InAs y P material, the composition y of As linearly changes from 0 to k, where 0 < k < 1; x Al 1-x As or InAs y P 1-y When growing In x Al 1-x As material, the composition x of In linearly changes from 0.52 to z, where 0.52 < z < 1; when growing InAs y P material, the composition y of As linearly changes from 0 to k, where 0 < k < 1; x Al 1-x As material, the composition x of In linearly changes from 0.52 to z, where 0.52 < z < 1; when growing InAs y P material, the composition y of As linearly changes from 0 to k, where 0 < k < 1; y P 1-y When growing InAs y P material, the composition y of As linearly changes from 0 to k, where 0 < k < 1; The thickness of the polished pseudo-substrate (2) is 4 μm.

9. The method for manufacturing the InGaAs detector structure as described in claim 6, characterized in that: Step 3 is to grow an InGaAs absorption layer (3) that matches the crystal lattice of the pseudo-substrate (2) on the treated pseudo-substrate (2) with a thickness of 3 μm.

10. The method for manufacturing the InGaAs detector structure as described in claim 6, characterized in that: The InAlAs cap layer (4) has a growth thickness of 1 μm.

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