GaN-based bidirectional dual-band avalanche photodetector based on back-to-back p-i-n structure

Abstract

The invention discloses a GaN-based bidirectional dual-waveband avalanche photodetector based on a back-to-back p-i-n structure, which comprises two back-to-back dual photodiode structures which share a p-type layer and grow on a substrate, namely a p-i-n structure taking GaN as an intrinsic layer and an SACM structure taking Al < 0.45 > Ga < 0.55 > N as an intrinsic layer. Compared with a traditional ultraviolet avalanche photodiode, the bidirectional dual-band avalanche photodiode can achieve avalanche multiplication under the forward bias voltage and the reverse bias voltage, and different working modes can be achieved by adjusting the external bias voltage. In a forward bias mode, the device is cut off at 365 nm, and in a reverse bias mode, the cut-off wavelength of the device is 281 nm, so that dual-band ultraviolet signal detection is realized, and the dual-band detection method is beneficial to accurate identification of signals and further popularization and application.

Description

Technical Field

[0001] The patent of this invention relates to the field of ultraviolet photoelectric detection technology, and specifically to a GaN-based bidirectional dual-band avalanche photodetector based on a back-to-back PIN structure. Background Art

[0002] In recent years, ultraviolet (UV) detection technology based on wide-bandgap semiconductor materials has significantly advanced the development of optoelectronics and improved traditional UV detection methods. This technology is crucial for information technology, environmental monitoring, and chemical and biological detection. Compared to traditional UV photomultiplier tubes (PMTs), nitride-based avalanche photodetectors (APDs) offer higher sensitivity, higher reliability, and lower noise. GaN and AlGaN, as important III-V nitride semiconductor materials, possess advantages such as wide bandgap, high breakdown field, low dark current, and electron-dominated avalanche. Consequently, they hold broad development potential and application potential in the field of avalanche photodiode UV detection. For AlGaN, the carrier impact ionization coefficient decreases with increasing Al content. At higher Al contents, the hole ionization coefficient exceeds the electron ionization coefficient, potentially enabling deep UV detection and single-carrier avalanche triggering, reducing excess device noise.

[0003] In ultraviolet photodetection, dual-band detection improves the signal-to-noise ratio by comparing wavelength variations, which is crucial for detecting low-concentration substances or weak signals. However, traditional GaN-based avalanche photodetectors, with their single-band detection, lack the precision to capture weak signals in complex environments. Therefore, achieving bidirectional, dual-band, low-noise detection using AlGaN and GaN heterostructures in a single device is crucial for improving the performance of avalanche photodetectors. Summary of the Invention

[0004] To address the above problems, the present invention provides a GaN-based bidirectional dual-band avalanche photodetector based on a back-to-back PIN structure, which utilizes AlGaN and GaN heterostructures in a single device to achieve bidirectional dual-band low-noise detection.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A GaN-based bidirectional dual-band avalanche photodetector based on a back-to-back PIN structure includes a PIN structure with GaN as the intrinsic layer and an Al 0.45 Ga 0.55 N is a SACM structure of an intrinsic layer, and the pin structure and the SACM structure are arranged back to back and share a p-type layer.

[0007] Preferably, the pin structure with GaN as the intrinsic layer is: p-Al 0.2 Ga0.8 N / i-GaN / n-GaN, p-Al 0.2 Ga 0.8 The thickness of N is 120nm, the thickness of i-GaN is 160-200nm, and the thickness of n-GaN is 120nm.

[0008] Preferably, the Al 0.45 Ga 0.55 The SACM structure with N as the intrinsic layer is: n-Al 0.5 Ga 0.5 N / i-Al 0.45 Ga 0.55 N / n-Al 0.45 Ga 0.55 N / i-Al 0.45 Ga 0.55 N / p-Al x Ga 1-x N / p-Al 0.2 Ga 0.8 N, of which p-Al x Ga 1-x The Al component of N changes gradually, and x changes from 0.45 to 0.2, close to i-Al 0.45 Ga 0.55 The x value on the N side is 0.45, where the p-Al 0.2 Ga 0.8 N is the p-Al in the pin structure 0.2 Ga 0.8 N layers.

[0009] Preferably, the thickness of each layer of the SACM structure is: n-Al 0.5 Ga 0.5 The thickness of N is 600nm, i-Al 0.45 Ga 0.55 The thickness of N is 180-200nm, n-Al 0.45 Ga 0.55 The thickness of N is 60nm, i-Al 0.45 Ga 0.55 The thickness of N is 180-200nm, p-Al x Ga 1-x N thickness is 60-100nm, p-Al 0.2 Ga 0.8 The thickness of N is 120 nm.

[0010] Preferably, the pin structure with GaN as the intrinsic layer is grown on a substrate, and the substrate is AlN / sapphire.

[0011] Beneficial effects:

[0012] The bidirectional, dual-band avalanche photodiode of the present invention can achieve avalanche multiplication in both forward and reverse bias modes, and different operating modes can be achieved by adjusting the applied bias voltage. In forward bias mode, the device cuts off at 365nm, while in reverse bias mode, its cutoff wavelength is 281nm, thus enabling dual-band ultraviolet signal detection. This dual-frequency detection method facilitates accurate signal identification and is conducive to further promotion and application. Specifically:

[0013] (1) In the forward mode, with positive incident light and forward bias voltage applied, the main active area of the device is the i-GaN intrinsic layer of the inverted pin structure avalanche photodiode, which absorbs ultraviolet light with a cutoff wavelength of 365nm and generates avalanche multiplication of photogenerated electron-hole pairs, which are then separated under the action of a strong electric field to generate a large current. The bottom SACM structure avalanche diode is forward-conducting, allowing the multiplied current generated by the upper pin structure avalanche diode to be detected unimpeded.

[0014] (2) In the reverse mode, the back incident light and reverse bias voltage are applied, and the main active area of the device is the i-Al of the reverse SACM structure avalanche photodiode. 0.45 Ga 0.55 N intrinsic layer, i-Al close to the substrate 0.45 Ga 0.55 N is the absorption layer, i-Al is far away from the substrate 0.45 Ga 0.55 N represents the avalanche multiplication layer. The absorption layer absorbs deep ultraviolet light with a cutoff wavelength of 281nm and generates photogenerated electron-hole pairs, which then separate under the action of a strong electric field. The high Al content in the AlGaN layer results in a greater impact ionization coefficient for holes than for electrons, making holes the dominant avalanche carriers. Photogenerated holes are driven from the absorption layer into the avalanche multiplication layer, triggering impact ionization and resulting in significant avalanche gain. The upper pin avalanche photodiode conducts forward, allowing the multiplied current generated by the lower SACM avalanche diode to be detected unimpeded. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 .Structural diagram (cross-sectional view) of a GaN-based bidirectional dual-band avalanche photodetector based on a back-to-back PIN structure of Example 1.

[0016] Figure 2 .Structural diagram (cross-sectional view) of the GaN-based avalanche photodetector based on the pin structure of Comparative Example 1.

[0017] Figure 3 .Structural diagram (cross-sectional view) of the AlGaN-based avalanche photodetector based on the SACM structure of Comparative Example 2.

[0018] Figure 4 .The electric field intensity and distribution and the impact ionization generation rate of the avalanche photodetector of Example 1 in the forward mode.

[0019] Figure 5 .The electric field intensity and distribution and the impact ionization generation rate of the avalanche photodetector of Example 1 in the reverse mode.

[0020] Figure 6 .Response spectra of the avalanche photodetector of Example 1 in forward and reverse modes.

[0021] Figure 7 .Response spectra of the avalanche photodetector of comparative example 1 in forward and reverse modes.

[0022] Figure 8 IV curves of the avalanche photodetector of Comparative Example 1 in forward and reverse modes.

[0023] Figure 9 .Response spectra of the avalanche photodetector of comparative example 2 in forward and reverse modes.

[0024] Figure 10 IV curves of the avalanche photodetector of Comparative Example 2 in forward and reverse modes.

[0025] Figure 1 Marking description: 1-AlN / sapphire substrate, 2-n-type Al 0.5 Ga 0.5 N layer, 3-intrinsic Al 0.45 Ga 0.55 N layer, 4-n type Al 0.45 Ga 0.55 N layer, 5-p type Al x Ga 1-x N (x: 0.2 to 0.45) layer, 6-p-type Al 0.2 Ga 0.8 N layer, 7-intrinsic GaN layer, 8-n-type GaN layer.

[0026] Figure 2 Marking description: 5-p type Al x Ga 1-x N (x: 0.2 to 0.45) layer, 6-p-type Al 0.2 Ga 0.8 N layer, 7-intrinsic GaN layer, 8-n-type GaN layer.

[0027] Figure 3 Marking Description: 2-n type Al 0.5 Ga 0.5 N layer, 3-intrinsic Al 0.45 Ga 0.55N layer, 4-n type Al 0.45 Ga 0.55 N layer, 5-p type Al x Ga 1-x N (x: 0.2 to 0.45) layer, 6-p-type Al 0.2 Ga 0.8 N layers. DETAILED DESCRIPTION

[0028] The accompanying drawings are for illustration purposes only and should not be construed as limiting the present invention. In order to better illustrate the embodiments, some parts of the accompanying drawings may be omitted or scaled, and do not represent the actual size of the device.

[0029] Example 1

[0030] like Figure 1 As shown, the avalanche photodetector device structure of the present invention is: substrate 1 / n-Al 0.5 Ga 0.5 N2 / i-Al 0.45 Ga 0.55 N3 / n-Al 0.45 Ga 0.55 N4 / i-Al 0.45 Ga 0.55 N3 / p-Al x Ga 1-x N(x:0.2~0.45)5 / p-Al 0.2 Ga 0.8 N6 / i-GaN7 / n-GaN8. The substrate is AlN / sapphire, that is, one layer of AlN and one layer of sapphire. The sapphire is in the direction away from the pin structure. The thickness of each layer is: n-Al 0.5 Ga 0.5 The thickness of N is 600nm, i-Al 0.45 Ga 0.55 The thickness of N is 180nm, n-Al 0.45 Ga 0.55 The thickness of N is 60nm, i-Al 0.45 Ga 0.55 The thickness of N is 180nm, p-Al x Ga 1-x N (x: 0.2 to 0.45) thickness 60nm, p-Al 0.2 Ga 0.8 The thickness of N is 120nm, the thickness of i-GaN is 160nm, and the thickness of n-GaN is 120nm. The material names and thicknesses of this structure are input into the simulation software Silvaco TCAD in sequence, and the electric field intensity and distribution, impact ionization generation rate and response spectrum are analyzed and calculated, as shown in the following example: Figure 4 、 Figure 5 and Figure 6 This embodiment realizes the detection of ultraviolet signals with a cutoff wavelength of 365 nm under positive pressure and the detection of deep ultraviolet signals with a cutoff wavelength of 281 nm under reverse pressure.

[0031] Comparative Example 1

[0032] like Figure 2 As shown, the pin GaN avalanche photodetector device structure of the present invention is: n-GaN8 / i-GaN7 / p-Al 0.2 Ga 0.8 N6 / p-Al x Ga 1-x N(x:0.2~0.45)5. The thickness of each layer is as follows: n-GaN thickness 120nm, i-GaN thickness 360nm, p-Al 0.2 Ga 0.8 The thickness of N is 120nm, p-Al x Ga 1-x The thickness of N (x: 0.2 to 0.45) is 60 nm. The material name and thickness of this structure are input into the simulation software Silvaco TCAD in sequence, and the response spectrum and IV curve of the pin GaN avalanche photodetector device structure are analyzed and calculated, as shown in the figure. Figure 7 and Figure 8 As shown. By observing the spectral response, it was found that the spectral response characteristics under both normal and back-incident light conditions are very similar, and the detection cutoff wavelength is 365nm, indicating that a single pin GaN avalanche photodetector device structure cannot achieve dual-band detection function. In addition, the device can only exhibit avalanche breakdown under forward bias (positive voltage applied to the n-GaN side) and exhibit forward conduction characteristics under reverse bias (no avalanche behavior), indicating that a single pin GaN avalanche photodetector device structure cannot achieve bidirectional detection function.

[0033] Comparative Example 2

[0034] like Figure 3 As shown, the SACM AlGaN avalanche photodetector device structure of the present invention is: p-Al 0.2 Ga 0.8 N6 / p-Al x Ga 1-x N(x:0.2~0.45)5 / i-Al 0.45 Ga 0.55 N / 3n-Al 0.45 Ga 0.55 N / 4i-Al 0.45 Ga 0.55 N3 / n-Al 0.5 Ga 0.5N2. The thickness of each layer is: p-Al 0.2 Ga 0.8 The thickness of N is 120nm, p-Al x Ga 1-x N (x: 0.2 to 0.45) thickness 60nm, i-Al 0.45 Ga 0.55 The thickness of N is 180nm, n-Al 0.45 Ga 0.55 The thickness of N is 60nm, i-Al 0.45 Ga 0.55 The thickness of N is 180nm, n-Al 0.5 Ga 0.5 The thickness of N is 600nm. The material name and thickness of this structure are input into the simulation software Silvaco TCAD in sequence, and the response spectrum and IV curve of the SACM AlGaN avalanche photodetector device structure are obtained by analysis and calculation, as shown in Figure 9 and Figure 10 As shown. By observing the spectral response, it is found that the spectral response characteristics under the two illumination conditions of normal incident light and back incident light are very similar, and the detection cutoff wavelength is 281nm, indicating that the single SACM AlGaN avalanche photodetector device structure cannot achieve dual-band detection function. In addition, the device can only be used under forward bias (n-Al 0.5 Ga 0.5 The device exhibits avalanche breakdown under a positive voltage on the N side and forward conduction characteristics under a reverse bias (no avalanche behavior occurs), indicating that a single SACMAlGaN avalanche photodetector device structure cannot achieve bidirectional detection function.

[0035] The above embodiments are preferred embodiments of the present invention, but the protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, any other modifications, simplifications and replacements should be included in the scope of protection of the claims of the present invention.

Claims

1. A GaN-based bidirectional dual-band avalanche photodetector based on a back-to-back PIN structure, comprising a PIN structure with GaN as an intrinsic layer, characterized in that Also includes Al 0.45 Ga 0.55 N is a SACM structure of an intrinsic layer, and the pin structure and the SACM structure are arranged back to back and share a P-type layer.

2. The GaN-based bidirectional dual-band avalanche photodetector according to claim 1, characterized in that: The pin structure with GaN as the intrinsic layer is: p-Al 0.2 Ga 0.8 N / i-GaN / n-GaN, p-Al 0.2 Ga 0.8 The thickness of N is 120nm, the thickness of i-GaN is 160-200nm, and the thickness of n-GaN is 120nm.

3. The GaN-based bidirectional dual-band avalanche photodetector according to claim 1 or 2, characterized in that: The Al 0.45 Ga 0.55 The SACM structure with N as the intrinsic layer is: n-Al 0.5 Ga 0.5 N / i-Al 0.45 Ga 0.55 N / n-Al 0.45 Ga 0.55 N / i-Al 0.45 Ga 0.55 N / p-Al x Ga 1-x N / p-Al 0.2 Ga 0.8 N, of which p-Al x Ga 1-x The Al component of N changes gradually, and x changes from 0.45 to 0.2, close to i-Al 0.45 Ga 0.55 The x value on the N side is 0.45, where the p-Al 0.2 Ga 0.8 N is the p-Al in the pin structure 0.2 Ga 0.8 N layers.

4. The GaN-based bidirectional dual-band avalanche photodetector according to claim 3, characterized in that: The thickness of each layer of SACM structure is as follows: n-Al 0.5 Ga 0.5 The thickness of N is 600nm, i-Al 0.45 Ga 0.55 The thickness of N is 180-200nm, n-Al 0.45 Ga 0.55 The thickness of N is 60nm, i-Al 0.45 Ga 0.55 The thickness of N is 180-200nm, p-Al x Ga 1-x N thickness is 60-100nm, p-Al 0.2 Ga 0.8 The thickness of N is 120 nm.

5. The GaN-based bidirectional dual-band avalanche photodetector according to claim 4, characterized in that: A pin structure with GaN as an intrinsic layer is grown on a substrate, which is AlN / sapphire.

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