Back irradiation absorption layer regulation and control doped ultraviolet detector

Abstract

The invention provides a back irradiation absorption layer regulation and control doping ultraviolet detector, which belongs to the technical field of semiconductor photoelectronic devices and comprises a P-type ohmic contact electrode, an N-type ohmic contact electrode, a substrate, a buffer layer, an N-type ohmic contact layer, an absorption layer and a P-type ohmic contact layer, and the substrate, the buffer layer, the N-type ohmic contact layer, the absorption layer and the P-type ohmic contact layer are sequentially distributed from bottom to top. The P-type ohmic contact electrode is located on the upper surface of the P-type ohmic contact layer, the N-type ohmic contact electrode is annular and located on the upper surface of the N-type ohmic contact layer, the absorption layer is located in the ring of the N-type ohmic contact electrode, and a thin P-type fully-depleted regulation and control doping layer is embedded in the absorption layer so that the absorption layer can be fully depleted; according to the invention, the collection efficiency of photon-generated carriers can be improved, and the response rate and the response speed are greatly improved, so that the performance of the ultraviolet detector can be improved, and the whole absorption region does not need to be compensated and doped.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and in particular to an absorption layer-regulated doping ultraviolet detector. Background Art

[0002] Ultraviolet (UV) detection technology, the third generation of photoelectric detection technology following radar and infrared detection, has demonstrated significant value in dual-use military and civilian applications. Leveraging its unique advantages within the electromagnetic spectrum, this technology has been widely applied in key areas such as sterilization, environmental monitoring, and industrial monitoring. Traditional UV detectors primarily utilize photomultiplier tubes (PMTs), which, while highly responsive, suffer from inherent limitations such as bulk, high power consumption, cathode cooling requirements, and poor mechanical stability, severely limiting their application.

[0003] With the development of wide-bandgap semiconductor technology, third-generation semiconductor materials, represented by AlGaN, offer new solutions for miniaturization and solid-state UV detectors. By adjusting the Al component, the AlGaN material system can achieve continuous control of the bandgap from 3.4 to 6.2 eV, enabling precise adjustment of the absorption cutoff wavelength within the range of 200 to 365 nm. Compared to traditional photomultiplier tubes, GaN-based detectors offer significant advantages such as compact size, high-temperature resistance, and immunity to visible light interference, making them particularly suitable for integrated applications such as UV focal plane arrays.

[0004] In terms of device structure, the PIN structure has become a research hotspot due to its excellent photoelectric conversion efficiency and photovoltaic working mode. 10 cm -3 ) can form an ideal high-resistance absorption layer. According to Poisson's equation, a uniform electric field is formed in the absorption region, so the photogenerated carriers generated in the absorption region are easily separated and output electrical signals, resulting in an ideal high response. However, in the actual growth process, due to the influence of crystal defects such as Si, O impurities and nitrogen vacancies, the background carrier concentration of unintentionally doped GaN is as high as 10 15 -10 17 cm -3. This high background concentration will significantly change the electric field distribution of the absorption layer, especially in the back-illuminated working mode (required for the flip-chip soldering process). The weakening of the electric field in the absorption layer near the N electrode will lead to two key problems: one is the reduction in the efficiency of collecting photogenerated carriers, and the other is the increase in the probability of recombination. In the prior art, the absorption layer full compensation doping technology proposed in the Chinese invention patent application "A PIN UV detector with compensation doping of the absorption layer" with publication number CN117410369A can effectively reduce the unintentional doping concentration in the absorption region and obtain a uniform electric field. However, the use of full compensation doping in the absorption region requires P-type compensation doping of the entire absorption region. Due to the difficulty of P-type doping, defects in the entire absorption region will inevitably be introduced. At the same time, doping of the entire absorption region increases the process difficulty and cost. This technical bottleneck seriously restricts the performance of AlGaN UV detectors in high-end applications such as focal plane arrays. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to solve the problem of decreased detector responsivity caused by background doping concentration in the absorption layer of a traditional detector without the need for compensatory doping of the entire absorption region.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions: a back-illuminated absorption layer regulated doping ultraviolet detector, the detector including a P-type ohmic contact electrode, an N-type ohmic contact electrode, and a substrate, a buffer layer, an N-type ohmic contact layer, an absorption layer, and a P-type ohmic contact layer distributed in sequence from bottom to top, the P-type ohmic contact electrode is located on the upper surface of the P-type ohmic contact layer, the N-type ohmic contact electrode is annular and is located on the upper surface of the N-type ohmic contact layer, the absorption layer is located within the ring of the N-type ohmic contact electrode, and a thin layer of P-type fully depleted regulated doping layer is embedded inside the ring to make the absorption layer fully depleted.

[0007] Beneficial effects: Conventional detectors usually have a very strong background doping concentration (10 15 -10 17 cm -3 ), these unintentionally doped carriers will affect the electric field distribution of the absorption layer and reduce the electric field of the absorption layer near the N electrode. When the working mode is back illumination, due to the large absorption coefficient of the AlGaN material, most of the light will be absorbed by the absorption layer near the N electrode, and the lack of the electric field will cause the photogenerated carriers to be unable to separate in time. It is difficult to be effectively absorbed by the electrode through diffusion alone, and most of them will be recombined. If the absorption layer is to be completely depleted, the thickness of the absorption layer must be reduced, but this will also lead to incomplete absorption of the incident light signal. The use of full compensation doping of the entire depletion region will introduce too many defects and increase the difficulty of the process.

[0008] The present invention introduces a thin layer of P-type fully depleted control doping layer into the absorption layer (no need to compensate for doping in the entire absorption region), which can regulate the electric field distribution inside the absorption layer, effectively improving the problem of uneven electric field distribution caused by high background doping, making the absorption layer fully depleted and the entire absorption layer full of electric field, sweeping the photogenerated carriers generated near the N electrode in the absorption layer out of the depletion region and being absorbed by the electrode, thereby improving the collection efficiency of the photogenerated carriers, greatly improving the response rate and response speed, and thus improving the performance of the ultraviolet detector.

[0009] Optimized, the P-type fully depleted control doping layer and the absorption layer have the same material but different doping. The position and intentional doping concentration of the P-type fully depleted control doping layer are jointly determined by the concentrations of the N-type ohmic contact layer and the P-type ohmic contact layer, the self-doping concentration of the P-type fully depleted control doping layer, and the unintentional doping concentration of the absorption layer.

[0010] Beneficial effects: In the present invention, the P-type fully depleted control doping layer is made of the same material as the absorption region, and the polarization effect of the heterojunction does not need to be considered, and the polarization electric field will 100% not be introduced.

[0011] Optimally, the P-type fully depleted control doping layer is located at 1 / 2 thickness of the absorption layer, or located between 1 / 2 thickness of the absorption layer and the bottom surface of the absorption layer and close to 1 / 2 thickness.

[0012] Optimized, non-intentionally doped Al absorber layer x Ga 1-x N material, 0≤x≤1, its unintentionally doped donor impurity concentration is 1.0×10 15 cm -3 -1.0×10 17 cm -3 ; The P-type fully depleted control doping layer is P-type intentionally doped Al x Ga 1-x N material, whose unintentionally doped donor impurity concentration is 1.0×10 15 cm -3 -1.0×10 17 cm -3 , the activation concentration of the intentionally doped acceptor impurities must be greater than the original unintentional doping concentration.

[0013] The optimized, unintentionally doped donor impurity concentration of the absorber layer is 5.0×10 16 cm -3 The doping concentration of the P-type fully depleted control doping layer is 1.0×10 18 cm -3 .

[0014] Optimized, P-type fully depleted control doping layer uses Mg ion compensation doped Al x Ga1-x Made of N material.

[0015] Optimally, the thickness of the absorption layer is 200-500 nanometers, and the thickness of the P-type fully depleted control doping layer is 1-10 nanometers.

[0016] Optimally, the substrate is made of planar sapphire or patterned sapphire or homogeneous gallium nitride, and the buffer layer is made of low-temperature epitaxial AlN material.

[0017] The optimized N-type ohmic contact layer is composed of high electron concentration N-type Al x Ga 1-x N material, 0≤x≤1, and its doping concentration is greater than 1×10 18 cm -3 .

[0018] The optimized P-type ohmic contact layer is made of P-type GaN material with high hole concentration, and its free hole concentration is 3.0×10 17 cm -3 .

[0019] The advantages provided by the present invention are:

[0020] 1. The UV detector of the present invention adopts a back-illuminated working mode, that is, light is incident from the end where the substrate is located, and is suitable for integrated application scenarios such as UV focal plane arrays.

[0021] 2. The preparation process of the present invention completely adopts standard LED technology. Compared with the traditional back-illuminated GaN-based PIN ultraviolet detector, the present invention does not require additional processing technology. It only needs to introduce a thin layer of fully depleted controlled doping during the epitaxial growth of the absorption layer, which will not introduce too many defects in the absorption region.

[0022] 3. The structural advantages of the present invention can be used in infrared and other band detectors, and the semiconductor materials used can be other high absorption coefficient materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a back-illuminated absorption layer-controlled doped ultraviolet detector provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram comparing the carrier concentration distribution of a back-illuminated absorption layer-doped UV detector regulated by an embodiment of the present invention with the carrier concentration distribution of a UV detector with a traditional structure;

[0025] Figure 3 A schematic diagram comparing the electric field intensity distribution of a back-illuminated absorption layer-doped UV detector provided by an embodiment of the present invention with the electric field intensity distribution of a conventional UV detector;

[0026] Figure 4 A schematic diagram comparing the spectral response of a back-illuminated absorption layer-modulated doped UV detector provided by an embodiment of the present invention with the spectral response of a conventional UV detector;

[0027] In the figure: 1 substrate, 2 buffer layer, 3 N-type ohmic contact layer, 4 absorption layer, 5 P-type fully depleted control doping layer, 6 P-type ohmic contact layer, 7 P-type ohmic contact electrode, 8 N-type ohmic contact electrode. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following describes the technical solutions of the present invention clearly and completely with reference to specific embodiments and the accompanying drawings. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, this embodiment provides a back-illuminated absorption layer controlled doping ultraviolet detector, including a P-type ohmic contact electrode 7, an N-type ohmic contact electrode 8, and a substrate 1, a buffer layer 2, an N-type ohmic contact layer 3, an absorption layer 4, and a P-type ohmic contact layer 6 grown and distributed in sequence from bottom to top. The P-type ohmic contact electrode 7 is located on the upper surface of the P-type ohmic contact layer 6, the N-type ohmic contact electrode 8 is annular and is located on the upper surface of the N-type ohmic contact layer 3, the absorption layer 4 is located in the ring of the N-type ohmic contact electrode 8, and a thin layer of P-type fully depleted controlled doping layer 5 is embedded inside the absorption layer 4 to make the absorption layer 4 fully depleted.

[0030] Conventional detectors usually have a very strong background doping concentration (10 15 -10 17 cm -3 ), these unintentionally doped carriers will affect the electric field distribution of the absorption layer and reduce the electric field of the absorption layer near the N electrode. When the working mode is back illumination, due to the large absorption coefficient of the AlGaN material, most of the light will be absorbed by the absorption layer near the N electrode, and the lack of the electric field will cause the photogenerated carriers to be unable to separate in time. It is difficult to be effectively absorbed by the electrode through diffusion alone, and most of them will be recombined. If the absorption layer is to be completely depleted, the thickness of the absorption layer must be reduced, but this will also lead to incomplete absorption of the incident light signal. The use of full compensation doping of the entire depletion region will introduce too many defects and increase the difficulty of the process.

[0031] By introducing a thin layer of P-type fully depleted control doping layer 5 into the absorption layer 4, the present invention can regulate the electric field distribution within the absorption layer 4, effectively improving the uneven electric field distribution problem caused by high background doping, making the absorption layer 4 fully depleted and the entire absorption layer 4 filled with an electric field. The photogenerated carriers generated near the N electrode of the absorption layer 4 are swept out of the depletion region and absorbed by the electrode, which can improve the collection efficiency of the photogenerated carriers, greatly improving the response rate and response speed, thereby improving the performance of the ultraviolet detector. The ultraviolet detector of the present invention adopts a back-illuminated operating mode, that is, light is incident from the end where the substrate 1 is located, and is suitable for integrated application scenarios such as ultraviolet focal plane arrays.

[0032] The substrate 1 is made of planar sapphire or patterned sapphire or homogeneous gallium nitride.

[0033] The buffer layer 2 is made of low-temperature epitaxial AlN material and has a thickness of 100 nanometers.

[0034] The N-type ohmic contact layer 3 is composed of N-type Al with high electron concentration. x Ga 1-x N material, where 0≤x≤1, and its doping concentration is greater than 1×10 18 cm -3 , with a thickness of 500 nanometers. In general, the doping concentration of the N-type ohmic contact layer 3 is selected to be 3×10 18 cm -3 .

[0035] The P-type fully depleted control doping layer 5 is made of the same material as the absorption layer 4, but with different doping. The position and intentional doping concentration of the P-type fully depleted control doping layer 5 are determined by the concentrations of the N-type ohmic contact layer 3 and the P-type ohmic contact layer 6, the inherent doping concentration of the P-type fully depleted control doping layer 5, and the unintentional doping concentration of the absorption layer 4. Since the P-type fully depleted control doping layer of the present invention is made of the same material as the absorption region, there is no need to consider the polarization effect of the heterojunction, and polarization electric fields are 100% eliminated.

[0036] The thickness of the absorption layer 4 is 200-500 nanometers, for example, the thickness of the absorption layer 4 can be set to 450 nanometers. The thickness of the P-type fully depleted control doping layer 5 is 1-10 nanometers, for example, the thickness of the P-type fully depleted control doping layer 5 can be set to 10 nanometers. The P-type fully depleted control doping layer 5 is located at 1 / 2 the thickness of the absorption layer 4, or between the 1 / 2 thickness of the absorption layer 4 and the bottom surface of the absorption layer 4 and close to the 1 / 2 thickness.

[0037] The absorption layer 4 is unintentionally doped Al x Ga 1-x N material, where 0≤x≤1, and its unintentionally doped donor impurity doping concentration is 1.0×10 15 cm -3 -1.0×1017 cm -3 ; P-type fully depleted control doping layer 5 is P-type intentionally doped Al x Ga 1- x N material, whose unintentionally doped donor impurity concentration is 1.0×10 15 cm -3 -1.0×10 17 cm -3 The P-type fully depleted control-doped layer 5 is embedded during the epitaxial growth of the absorber layer 4. It is doped with an acceptor impurity at a higher activation concentration than the unintentional donor concentration. This means the activation concentration of the intentionally doped acceptor impurity must be greater than the original unintentional doping concentration. The control-doped layer embedded in the absorber layer 4 is a P-type fully depleted control-doped layer with carriers of opposite electrical properties to the intentionally doped layer. Compensatory doping results in inversion of this layer.

[0038] The unintentionally doped donor impurity concentration of the absorption layer 4 is 5.0×10 16 cm -3 The doping concentration of the P-type fully depleted control doping layer 5 is 1.0×10 18 cm -3 .

[0039] The P-type fully depleted control doping layer 5 is compensated by Mg ion doping of Al x Ga 1-x Made of N material.

[0040] The P-type ohmic contact layer 6 is made of a P-type GaN material with a high hole concentration, and its free hole concentration is 3.0×10 17 cm -3 , with a thickness of 70-150 nanometers.

[0041] Figure 2 This is a comparison result of the carrier concentration distribution along the epitaxial direction of a back-illuminated absorption layer-controlled doped ultraviolet detector of the present invention with that of a traditional PIN ultraviolet detector. It can be seen that within the absorption layer, the present invention only adds a thin layer of P doping, which will not have much impact on the entire depletion region.

[0042] Figure 3This is a comparison result of the electric field intensity distribution along the epitaxial direction of a back-illuminated absorption layer-regulated doped ultraviolet detector of the present invention and a traditional PIN ultraviolet detector. It can be seen that within the absorption layer, the electric field of the back-illuminated absorption layer-regulated doped ultraviolet detector extends to the entire absorption region, and the P-type fully depleted regulated doped layer 5 has been completely depleted. The absorption layer-regulated doped ultraviolet detector is more conducive to the separation of photogenerated carriers in the entire absorption layer. However, since the electric field of the traditional structure detector is very low near the N electrode of the absorption layer, a large number of carriers will be recombined before being converted into signals, so the responsiveness is lower than that of the new structure.

[0043] Figure 4 The comparison results of the spectral response of the back-illuminated absorption layer-controlled doped UV detector of the present invention and the traditional PIN UV detector show that within the entire spectral response range, the absorption layer-compensated doped PIN UV detector has a larger spectral response value, and the response at the response peak is improved by about 25%. The reason for the high response rate of the detector of the present invention is that when ultraviolet light is incident from the substrate 1, due to the large absorption coefficient of the GaN material, a large amount of ultraviolet light will be absorbed near the N-electrode in the absorption layer when back-illuminated. However, in the traditional structure detector, the GaN grown by the unintentional doping of the absorption layer has a very strong background doping concentration. These unintentional doped carriers will hinder the depletion width of the absorption layer, affect the electric field distribution of the absorption layer, and reduce the electric field of the absorption layer near the N-electrode. Most of the light will be absorbed by the absorption layer near the N-electrode, and the lower electric field will cause a large number of photogenerated carriers to be quickly recombined, reducing the signal current. Inserting a P-type fully depleted control layer into the absorption layer can modulate the electric field distribution, resulting in full depletion of the absorption layer. This fills the entire absorption layer with an electric field, sweeping photogenerated carriers generated near the N-electrode out of the depletion region and being absorbed by the electrode, significantly improving both the responsivity and response speed. The present invention achieves a higher spectral responsivity by fully depleting the P-type fully depleted control doped layer 5 and the entire absorption layer 4. This also increases the detector's response speed while maintaining the spectral responsivity.

[0044] Compared to traditional PIN-structured UV detectors, this invention introduces a thin fully depleted, regulated doping layer into region I (the absorption layer), thereby fully depleting the absorption region. This improves the UV detector's spectral responsivity and significantly enhances device performance. The fabrication process utilizes standard LED technology. Compared to traditional back-illuminated GaN-based PIN UV detectors, this invention requires no additional processing, requiring only a thin layer of fully depleted, regulated doping during the epitaxial growth of the absorption layer, which minimizes the introduction of excessive defects in the absorption region.

[0045] In addition, the structural advantages of the back-illuminated absorption layer-controlled doped ultraviolet detector of the present invention can be used for infrared and other band detectors, and the semiconductor materials used can be other high absorption coefficient materials.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A back-illuminated absorber-controlled doped UV detector, characterized by: The detector comprises a P-type ohmic contact electrode (7), an N-type ohmic contact electrode (8), and a substrate (1), a buffer layer (2), an N-type ohmic contact layer (3), an absorption layer (4), and a P-type ohmic contact layer (6) which are sequentially distributed from bottom to top. The P-type ohmic contact electrode (7) is located on the upper surface of the P-type ohmic contact layer (6). The N-type ohmic contact electrode (8) is annular and located on the upper surface of the N-type ohmic contact layer (3). The absorption layer (4) is located within the ring of the N-type ohmic contact electrode (8), and a thin layer of P-type fully depleted control doping layer (5) is embedded in the absorption layer (4) to fully deplete the absorption layer (4).

2. The back-illuminated absorption layer controlled doped UV detector according to claim 1, characterized in that: The P-type fully depleted control doping layer (5) and the absorption layer (4) are made of the same material but have different doping. The position and intentional doping concentration of the P-type fully depleted control doping layer (5) are determined by the concentrations of the N-type ohmic contact layer (3) and the P-type ohmic contact layer (6), the self-doping concentration of the P-type fully depleted control doping layer (5), and the unintentional doping concentration of the absorption layer (4).

3. The back-illuminated absorption layer-controlled doped UV detector according to claim 1 or 2, characterized in that: The P-type fully depleted control doping layer (5) is located at 1 / 2 thickness of the absorption layer (4), or is located between 1 / 2 thickness of the absorption layer (4) and the bottom surface of the absorption layer (4) and close to 1 / 2 thickness.

4. The back-illuminated absorption layer-controlled doped UV detector according to claim 1 or 2, characterized in that: The absorption layer (4) is unintentionally doped Al x Ga 1-x N material, 0≤x≤1, its unintentionally doped donor impurity concentration is 1.0×10 15 cm -3 -1.0×10 17 cm -3 ; The P-type fully depleted control doping layer (5) is a P-type intentionally doped Al x Ga 1-x N material, whose unintentionally doped donor impurity concentration is 1.0×10 15 cm -3 -1.0×10 17 cm -3 , the activation concentration of the intentionally doped acceptor impurities must be greater than the original unintentional doping concentration.

5. The back-illuminated absorption layer-controlled doped UV detector according to claim 4, characterized in that: The unintentionally doped donor impurity concentration of the absorption layer (4) is 5.0×10 16 cm -3 The doping concentration of the P-type fully depleted control doping layer (5) is 1.0×10 18 cm -3 .

6. The back-illuminated absorption layer-controlled doped UV detector according to claim 4, characterized in that: The P-type fully depleted control doping layer (5) is made of Al2O3 doped with Mg ions. x Ga 1-x Made of N material.

7. The back-illuminated absorption layer-controlled doped UV detector according to claim 1, characterized in that: The thickness of the absorption layer (4) is 200-500 nanometers, and the thickness of the P-type fully depleted control doping layer (5) is 1-10 nanometers.

8. The back-illuminated absorption layer-controlled doped ultraviolet detector according to claim 1, characterized in that: The substrate (1) is made of planar sapphire or patterned sapphire or homogeneous gallium nitride, and the buffer layer (2) is made of low-temperature epitaxial AlN material.

9. The back-illuminated absorption layer controlled doped UV detector according to claim 1, characterized in that: The N-type ohmic contact layer (3) is composed of N-type Al with high electron concentration. x Ga 1-x N material, 0≤x≤1, and its doping concentration is greater than 1×10 18 cm -3 .

10. The back-illuminated absorption layer controlled doping ultraviolet detector according to claim 1, characterized in that: The P-type ohmic contact layer (6) is made of a P-type GaN material with a high hole concentration, and its free hole concentration is 3.0×10 17 cm -3 .

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