A single photon avalanche detector with improved detection rate and a method of manufacturing the same

Abstract

The application discloses a single-photon avalanche detector with improved detection rate and a preparation method thereof. 1‑x In x As / InP / Al 1‑y In y As strained layer, GaInAs absorption layer, periodic Al 1‑z In z As / InP / Al 1‑t In t As band transition layer, InP charge layer, Al 1‑z In z As multiplication layer and InP diffusion layer. The application can effectively reduce the heterojunction interface defects of the InP buffer layer and the GaInAs absorption layer, eliminate the valence band step of the interface of the InP buffer layer and the GaInAs absorption layer, and thus improve the detection rate of the detector.

Description

Technical Field

[0001] This invention relates to the technical field of single-photon avalanche detectors, and in particular to a single-photon avalanche detector with improved detectivity and its fabrication method. Background Technology

[0002] InGaAs / InP single-photon avalanche detectors and related quenching electronics have seen rapid development in recent years, with mature detector products achieving detection efficiencies exceeding 20% ​​at a wavelength of 1550 nm. Compared to photomultiplier tube single-photon detectors and superconducting nanowire single-photon detectors, semiconductor single-photon detectors offer advantages such as small size, low cost, ease of system integration, and excellent overall performance, making them the preferred solution for practical applications.

[0003] InP-based SPADs exhibit high spectral response characteristics, and the band gap of the InGaAs absorption layer is tunable, ranging from 0.75 to 1.42 eV, covering the telecommunications band (1310 / 1550 nm), with an absorption coefficient as high as 10. 4 The density of InP is 100 times that of silicon (cm⁻¹). Furthermore, InP has a better ionization coefficient in the avalanche region than silicon, resulting in more uniform avalanche triggering and thus higher gain. Compared to silicon-based SPADs, InP devices can achieve a dark count rate (DCR) of less than 1 kcps (1550 nm) at -30°C. InP-based single-photon avalanche detectors (SPADs) are core devices for near-infrared (900-1700 nm) single-photon detection, and are irreplaceable, especially in fields such as quantum communication (1550 nm), lidar, and bioimaging.

[0004] However, the InGaAs / InP interface exhibits a 0.08% lattice mismatch, which leads to non-uniform avalanche gain, increased dark current, and increased fluctuations in photon detection efficiency (PDE). Therefore, improving defects in heterogeneous materials is crucial for detector fabrication. Utilizing defect control techniques to improve the dark count and further enhance the PDE has become a key research direction for improving the performance of InGaAs / InP single-photon avalanche detectors. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-photon avalanche detector with improved detectivity and its fabrication method, which can effectively reduce the dark count and afterpulse of the detector and effectively improve the device detectivity.

[0006] The objective of this invention is achieved through the following technical solution: A single-photon avalanche detector with improved detectivity includes a single-sided polished InP substrate and an InP buffer layer and periodic Al atoms grown sequentially from bottom to top on the front side of the single-sided polished InP substrate.1-x In x As / InP / Al 1-y In y As strain layer, GaInAs absorption layer, periodic Al 1-z In z As / InP / Al 1-t In t As bandgap transition layer, InP charge layer, Al 1-z In z As multiplication layer and InP diffusion layer, through periodic Al 1-x In x As / InP / Al 1-y In y As strain layer combined with periodic Al 1-z In z As / InP / Al 1-t In t The As bandgap transition layer effectively reduces interface defects at the heterojunction of the InP buffer layer and the GaInAs absorption layer, and eliminates the valence band step at the interface of the InP buffer layer and the GaInAs absorption layer, thereby improving the detector's detectivity.

[0007] Furthermore, the InP buffer layer has a growth thickness of 200~600nm, a growth rate of 2~5Å / s, and a growth temperature of 580~610℃.

[0008] Furthermore, the periodic Al 1-x In x As / InP / Al 1-y In y The As strain layer consists of several periodically arranged Al layers. 1-x In x As layer, InP layer and Al 1-y In y As layer, Al 1-x In x As layer and Al 1-y In y The As layer has a growth thickness of 5~15 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The x and y components are 0.45~0.55.

[0009] Furthermore, the GaInAs absorber layer has a growth thickness of 1500~2500 nm, a growth rate of 4~7 Å / s, and a growth temperature of 600~650 °C.

[0010] Furthermore, the periodic Al 1-zIn z As / InP / Al 1-t In t The As band transition layer consists of several periodically arranged Al groups. 1-z In z As layer, InP layer and Al 1-t In t As layer, the Al 1-z In z As layer and Al 1-t In t The As layer has a growth thickness of 3~10 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The z and t components are 0.45~0.55.

[0011] Furthermore, the InP charge layer has a growth thickness of 1000~2000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610 °C.

[0012] Furthermore, the Al 1-z In z The As multiplication layer has a growth thickness of 200~600 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

[0013] Furthermore, the InP diffusion layer has a growth thickness of 2000~4000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610 °C.

[0014] A method for fabricating a single-photon avalanche detector with improved detectivity, comprising the following steps: S1. An InP buffer layer and periodic Al are grown sequentially from bottom to top on the front side of a single-sided polished InP substrate. 1- x In x As / InP / Al 1-y In y As strain layer, GaInAs absorption layer, periodic Al 1-z In z As / InP / Al 1-t In t As bandgap transition layer, InP charge layer, Al 1-z In z The prepared epitaxial structure was obtained by adding an As multiplication layer and an InP diffusion layer. S2. A high-temperature resistant dielectric film SiN is grown on an epitaxial substrate, and then diffusion holes are processed by photolithography etching technology to obtain a chip with diffusion holes. S3. Perform Zn diffusion on the chip with the diffusion holes processed to form the P region; S4. After diffusion, the chip is annealed in a pure nitrogen atmosphere at 480℃ for 5 minutes. Then, the inside of the diffusion hole is micro-processed with an acidic solution to reduce the high defect layer on the upper surface of the diffusion area and avoid the formation of leakage channels under high voltage. S5. The chip is subjected to sulfur treatment to form a passivation layer, and the SiO2 passivation layer is grown by PECVD equipment. S6. Contact holes and P / N electrodes are fabricated on the chip using photolithography, etching, and vapor deposition to complete the fabrication.

[0015] Furthermore, in step S3, the diffusion temperature is 500~550℃, the diffusion pressure is 60~140Tor, the diffusion time is 1000~2000s, and the diffusion flow rate is 60~130cc.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention introduces periodic Al 1-x In x As / InP / Al 1-y In y As strain layer combined with periodic Al 1-z In z As / InP / Al 1-t In t By using an As bandgap transition layer, the surface properties and lattice integrity are improved while smoothing the bandgap transition between GaInAs and InP, enabling the growth of high-quality InGaAs epitaxial materials, reducing the defect density in the GaInAs absorption layer, optimizing device detectivity, and improving device performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the single-photon avalanche detector of the present invention.

[0018] Figure 2 This is a schematic diagram of the growth of a dielectric film and the fabrication of diffusion holes on an epitaxial substrate according to the present invention.

[0019] Figure 3 This is a schematic diagram illustrating the Zn diffusion process of the present invention.

[0020] Figure 4 This is a comparison chart of PDE tests for single-photon avalanche detectors. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example 1: like Figure 1 As shown, this embodiment provides a single-photon avalanche detector with improved detectivity, including a single-sided polished InP substrate 1 and an InP buffer layer 2 and periodic Al2O3 layers grown sequentially from bottom to top on the front side of the single-sided polished InP substrate. 1-x In x As / InP / Al 1-y In y As strain layer 3, GaInAs absorption layer 4, periodic Al 1-z In z As / InP / Al 1-t In t 5. As bandgap transition layer, 6. InP charge layer, Al 1-z In z As multiplication layer 7 and InP diffusion layer 8, through periodic Al 1-x In x As / InP / Al 1- y In y As strain layer combined with periodic Al 1-z In z As / InP / Al 1-t In t The As bandgap transition layer effectively reduces interface defects at the heterojunction of the InP buffer layer and the GaInAs absorption layer, and eliminates the valence band step at the interface of the InP buffer layer and the GaInAs absorption layer, thereby improving the detector's detectivity.

[0023] The InP buffer layer is grown to a thickness of 200~600 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

[0024] Periodic Al 1-x In x As / InP / Al 1-y In y The As strain layer consists of several periodically cyclically arranged Al layers (taking 10 to 30 as an example). 1-x In x As layer, InP layer and Al 1-y Iny As layer, Al 1-x In x As layer and Al 1-y In y The As layer has a growth thickness of 5~15 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The x and y components are 0.45~0.55.

[0025] The GaInAs absorber layer is grown to a thickness of 1500~2500 nm, a growth rate of 4~7 Å / s, and a growth temperature of 600~650℃.

[0026] Periodic Al 1-z In z As / InP / Al 1-t In t The As band transition layer consists of several (taking 10 to 50 as an example) periodically arranged Al groups. 1-z In z As layer, InP layer and Al 1-t In t As layer, the Al 1-z In z As layer and Al 1-t In t The As layer has a growth thickness of 3~10 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The z and t components are 0.45~0.55.

[0027] The InP charge layer has a growth thickness of 1000~2000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

[0028] Al 1-z In z The As multiplication layer has a growth thickness of 200~600 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

[0029] The InP diffusion layer is grown to a thickness of 2000~4000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

[0030] The InP lattice constant is 5.8687 Å, and the InGaAs target layer lattice constant is 5.8693 Å, with a mismatch rate of ≈0.01%, which seems small. However, stress will still accumulate in the heteroepitaxial layer, leading to dislocations. Traditional structures would directly grow a GaInAs epitaxial layer larger than 1 μm to concentrate and release this mismatch, thus easily forming a density >10. 6 cm -2 The penetration dislocations lead to an increased dark count rate (DCR). This invention utilizes periodic Al growth... 1-x In x As / InP / Al 1-y In y As strain layer improves the crystal quality of GaInAs absorption layer, while also mitigating the tensile stress caused by the difference in thermal expansion coefficients between InP and GaInAs, effectively buffering the interface stress between InP and GaInAs, reducing the formation of through dislocations, and lowering the material's DCR.

[0031] Traditional SPADs commonly use In x Ga 1-x As y P 1-y As a band transition, this invention employs Al 1-z In z As / InP / Al 1- t In t As is used to adjust the Al composition in AlInAs, causing the band gap to gradually change from 1.35 eV to 1.45 eV, transitioning from the InP band to the AlInAs band, thus eliminating the valence band step (ΔE) at the InGaAs / InP interface. v (≈0.38 eV) and reduced interfacial recombination losses improve hole injection efficiency. Additionally, Al is used... 1-z In z As / InP / Al 1-t In t As a superlattice structure, the As-type structure acts as a band transition layer, blocking the stepwise relaxation of strain and dislocation bending at the GaInAs / AlInAs interface. By "sweeping away" the "roadblocks" on the path of crystal defects, it ensures that photogenerated carriers can reach the avalanche region safely and to the maximum extent, thereby triggering an avalanche signal. This achieves efficient controllability of process parameters and improves the device's PDE.

[0032] Example 2: This embodiment provides a method for fabricating the single-photon avalanche detector with improved detectivity as described in Embodiment 1, including the following steps: S1. Using MOCVD or MBE technology, grow an InP buffer layer and periodically formed Al layers sequentially from bottom to top on the front side of a single-sided polished InP substrate. 1-x Inx As / InP / Al 1-y In y As strain layer, GaInAs absorption layer, periodic Al 1-z In z As / InP / Al 1- t In t As bandgap transition layer, InP charge layer, Al 1-z In z An As multiplication layer and an InP diffusion layer were added to obtain the prepared epitaxial structure, such as... Figure 1 As shown; S2. A high-temperature resistant dielectric film SiN 9 is grown on the epitaxial substrate by PECVD, and then diffusion holes 10 are fabricated by photolithography etching technology, such as... Figure 2 As shown, a chip with diffusion holes is obtained; S3. Zn diffusion is performed on the chip with the prepared diffusion holes using MOCVD to form a P-region, such as... Figure 3 As shown; wherein, the diffusion temperature is 500~550℃, the diffusion pressure is 60~140Tor, the diffusion time is 1000~2000s, and the diffusion flow rate is 60~130cc; S4. After diffusion, the chip is annealed in a pure nitrogen atmosphere at 480℃ for 5 minutes. Then, the inside of the diffusion hole is micro-processed with an acidic solution to reduce the high defect layer on the upper surface of the diffusion area and avoid the formation of leakage channels under high voltage. S5. The chip is subjected to sulfidation treatment by electrochemical process to form a passivation layer, and the SiO2 passivation layer is grown by PECVD machine. S6. Using conventional semiconductor technologies such as photolithography, etching, and vapor deposition, contact holes and P / N electrodes are fabricated on the chip to complete the preparation.

[0033] Comparative Example 1: The difference between this embodiment and Embodiment 2 is that: the periodic Al... 1-x In x As / InP / Al 1-y In y The strain layer is removed, while the other growth conditions remain unchanged.

[0034] Comparative Example 2: The difference between this embodiment and Embodiment 2 is that: the periodic Al... 1-z In z As / InP / Al 1-t In tThe As band transition layer is changed to the barrier layer structure in a single-photon detector and its fabrication method (CN109148636A), while the other growth conditions remain unchanged.

[0035] PDE and DCR were tested on Example 2, Comparative Example 1, and Comparative Example 2. The test results are as follows: Figure 4 As shown, at a low temperature of -40°C, the DCR of Example 2 is as low as 12 kHz, and the PDE increases to 26%, which is a significant improvement compared to the conventional structures of Comparative Example 1 and Comparative Example 2.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A single-photon avalanche detector with improved detectivity, characterized in that: This includes a single-sided polished InP substrate and an InP buffer layer and periodic Al layers grown sequentially from bottom to top on the front side of the single-sided polished InP substrate. 1-x In x As / InP / Al 1- y In y As strain layer, GaInAs absorption layer, periodic Al 1-z In z As / InP / Al 1-t In t As bandgap transition layer, InP charge layer, Al 1-z In z As multiplication layer and InP diffusion layer, through periodic Al 1-x In x As / InP / Al 1-y In y As strain layer combined with periodic Al 1-z In z As / InP / Al 1-t In t The As bandgap transition layer effectively reduces interface defects at the heterojunction of the InP buffer layer and the GaInAs absorption layer, and eliminates the valence band step at the interface of the InP buffer layer and the GaInAs absorption layer, thereby improving the detector's detectivity.

2. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The InP buffer layer has a growth thickness of 200~600nm, a growth rate of 2~5Å / s, and a growth temperature of 580~610℃.

3. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The periodic Al 1-x In x As / InP / Al 1-y In y The As strain layer consists of several periodically arranged Al layers. 1-x In x As layer, InP layer and Al 1- y In y As layer, Al 1-x In x As layer and Al 1-y In y The As layer has a growth thickness of 5~15 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The x and y components are 0.45~0.

55.

4. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The GaInAs absorber layer has a growth thickness of 1500~2500 nm, a growth rate of 4~7 Å / s, and a growth temperature of 600~650 °C.

5. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The periodic Al 1-z In z As / InP / Al 1-t In t The As band transition layer consists of several periodically arranged Al groups. 1-z In z As layer, InP layer and Al 1-t In t As layer, the Al 1-z In z As layer and Al 1-t In t The As layer has a growth thickness of 3~10 nm, a growth rate of 3~8 Å / s, and a growth temperature of 600~650℃. The InP layer has a growth thickness of 3~10 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃. The z and t components are 0.45~0.

55.

6. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The InP charge layer has a growth thickness of 1000~2000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

7. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The Al 1-z In z The As multiplication layer has a growth thickness of 200~600 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

8. The single-photon avalanche detector with improved detectivity according to claim 1, characterized in that: The InP diffusion layer has a growth thickness of 2000~4000 nm, a growth rate of 2~5 Å / s, and a growth temperature of 580~610℃.

9. The method for fabricating a single-photon avalanche detector with improved detectivity according to any one of claims 1 to 8, characterized in that, Including steps, S1. An InP buffer layer and periodic Al are grown sequentially from bottom to top on the front side of a single-sided polished InP substrate. 1-x In x As / InP / Al 1-y In y As strain layer, GaInAs absorption layer, periodic Al 1-z In z As / InP / Al 1-t In t As bandgap transition layer, InP charge layer, Al 1-z In z The prepared epitaxial structure was obtained by adding an As multiplication layer and an InP diffusion layer. S2. A high-temperature resistant dielectric film SiN is grown on an epitaxial substrate, and then diffusion holes are processed by photolithography etching technology to obtain a chip with diffusion holes. S3. Perform Zn diffusion on the chip with the diffusion holes processed to form the P region; S4. After diffusion, the chip is annealed in a pure nitrogen atmosphere at 480℃ for 5 minutes. Then, the inside of the diffusion hole is micro-processed with an acidic solution to reduce the high defect layer on the upper surface of the diffusion area and avoid the formation of leakage channels under high voltage. S5. The chip is subjected to sulfur treatment to form a passivation layer, and the SiO2 passivation layer is grown by PECVD equipment. S6. Contact holes and P / N electrodes are fabricated on the chip using photolithography, etching, and vapor deposition to complete the fabrication.

10. The method for fabricating a single-photon avalanche detector with improved detectivity according to claim 9, characterized in that, In step S3, the diffusion temperature is 500~550℃, the diffusion pressure is 60~140 Torr, the diffusion time is 1000~2000s, and the diffusion flow rate is 60~130cc.

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