InGaN-based visible light detector

Abstract

The invention discloses an InGaN-based visible light detector. The InGaN-based visible light detector comprises a substrate; the n-type layer is located on the substrate; the active layer is located on the n-type layer; the active layer is formed by periodically stacking a plurality of unit structures, and each unit structure comprises an In < x > Ga < 1-x > N absorption layer with a high In component, a cover layer and a GaN quantum barrier layer which grow in sequence; the cover layer is composed of a GaN cover layer and an Al < y > Ga < 1-y > N cover layer; the active layer is provided with a V-shaped pit, the V-shaped pit penetrates through the whole active layer, and the V-shaped pit comprises a V-shaped pit side wall and a V-shaped pit platform; and the p-type layer is positioned on the active layer. The cover layer is grown on the In < x > Ga < 1-x > N absorption layer to protect the In < x > Ga < 1-x > N absorption layer, so that the damage to the In < x > Ga < 1-x > N absorption layer caused by the temperature rise process of the subsequent growth of the GaN quantum barrier layer and the p-type layer is reduced. Meanwhile, the leakage current of the detector is effectively suppressed, the dark current of the device is reduced, and the performance of the detector is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of visible light detectors, and in particular to an InGaN-based visible light detector. Background Art

[0002] Visible light detectors, as detection devices that can convert visible light signals into electrical signals, play an extremely wide and critical role in both military and civilian fields. As one of the research hotspots of third-generation semiconductor materials, InGaN materials have excellent physical and chemical properties, such as high electron mobility, excellent thermal stability and chemical stability. By adjusting the In composition in the alloy, its band gap can be continuously changed in the range of 3.4 eV to 0.7 eV, which enables InGaN detectors to achieve continuous detection of the entire visible light band. Compared with traditional visible light detectors, InGaN detectors have significant advantages such as small size, easy integration, high breakdown electric field (>1 MV / cm), low operating voltage and no need for filtering systems.

[0003] In InGaN-based visible light detectors, dark current is a key parameter determining device performance and directly impacting the detector's detectivity. Given that the mechanisms responsible for dark current vary under different detector conditions, targeted process techniques are needed to further suppress it. Currently, in chip manufacturing, a common method for suppressing dark current is to grow SiO2, SiN, or other dielectric passivation films to block leakage channels. However, leakage stems from material defects. Suppressing this leakage at the material growth stage would not only achieve superior detector performance but also reduce chip manufacturing costs.

[0004] Chinese invention patent CN116364800A discloses an InGaN visible light detector epitaxial structure with both high responsivity and high response speed. The epitaxial structure includes a substrate, a buffer layer, an n-type GaN layer, a V-shaped pit opening layer, an InGaN / GaN quantum well layer, and a p-type Al x Ga 1-x N layer and p-type GaN layer; in the V-pit opening layer, a V-shaped pit is created along the dislocation line. The V-pit consists of a terrace and sidewalls. By manipulating the V-pit shape, both response speed and responsivity are improved. However, this epitaxial structure has certain limitations and is only suitable for absorber layers with low indium content. If the indium content in the InGaN / GaN quantum well layer is high, the detector's dark current will remain high.

[0005] It should be noted that the information disclosed in this background technology section is only used to enhance the understanding of the overall background of the invention and should not be regarded as an admission or any form of implication that this information is already prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide an InGaN-based visible light detector.

[0007] The object of the present invention is achieved like this: The present invention provides an InGaN-based visible light detector, comprising: substrate; an n-type layer located on the substrate; The active layer is located on the n-type layer; the active layer is composed of multiple unit structures stacked periodically, each unit structure includes InxGa with high In content grown sequentially 1-x N absorption layer, cap layer and GaN quantum barrier layer; the cap layer consists of GaN cap layer and Al y Ga 1- y The active layer is composed of an N cap layer; the active layer has a V-pit, which runs through the entire active layer and includes a V-pit sidewall and a V-pit platform; The p-type layer is located on the active layer.

[0008] The principle of suppressing dark current in the visible light detector provided by the present invention is as follows: In the prior art, it is usually directly in the In high In content x Ga 1-x GaN quantum barrier layer and p-type layer are grown on the N absorption layer. On the one hand, the In with high In content x Ga 1-x There is a large lattice mismatch between the N absorption layer and the GaN quantum barrier layer, which will lead to the x Ga 1-x The crystal quality of the N absorption layer deteriorates, resulting in a decrease in device performance. At the same time, defects will increase and a large number of leakage channels will be generated. The piezoelectric polarization in the InGaN absorption layer will cause the energy band to tilt, resulting in a more serious spatial separation of photogenerated electrons and holes. Large stress will easily lead to InGaN x Ga 1-x More metal In precipitation and phase separation occur inside the N absorption layer, which leads to an increase in dark current. On the other hand, when growing the GaN quantum barrier layer and the p-type layer, the temperature needs to be increased, which leads to In x Ga 1-x Metal In is precipitated in the N absorption layer.

[0009] In the present invention, the GaN cap layer and the Al y Ga 1-y N cap layer to protect In x Ga 1-xN absorption layer, since the subsequent growth of GaN quantum barrier layer and p-type layer requires higher temperature, the heating process and subsequent high temperature growth process x Ga 1-x The damage caused by the N absorption layer directly exposes In x Ga 1-x The N absorption layer will cause In volatilization or lattice damage at high temperature. The GaN cap layer is grown at a relatively low temperature to form a physical barrier, which improves the interface quality and can also isolate the high temperature process from the In. x Ga 1-x Destruction of the N absorption layer. Wide bandgap Al y Ga 1-y The N cap layer can form an electron / hole blocking barrier to partially offset the In x Ga 1-x The polarization electric field of the N absorption layer reduces the accumulation of interface charges, achieves the matching of the polarization electric field, and reduces the polarization effect. y Ga 1-y The conduction band offset of the N cap layer can inhibit the electrons from flowing from the n-type layer to the In x Ga 1-x Back diffusion of the N absorption layer, which is usually the main source of dark current in the detector. In addition, the crystal quality of the material can be improved by compensating for strain. x Ga 1-x N absorption layer and Al y Ga 1-y Adding a relatively thin GaN cap layer between the N cap layers can provide a basis for growing high-quality Al y Ga 1-y The N cap layer lays a good foundation, achieves the effect of balancing stress and lattice matching, reduces the influence of polarization electric field, and reduces polarization effect.

[0010] Optional, In x Ga 1-x In the N absorption layer, the value range of x is 0.3 ≤ x ≤ 0.6.

[0011] Optionally, the GaN cap layer has a thickness in the range of 0.5 nm to 1 nm, inclusive.

[0012] Optional, Al y Ga 1-y The thickness of the N cap layer ranges from 0.5 nm to 2 nm, inclusive.

[0013] Optional, Al y Ga 1-y In the N cap layer, the value range of y is 0.1 ≤ y ≤ 0.4.

[0014] Optional, In x Ga1-x The band gap width of the N absorption layer at the side wall of the V pit is larger than that of the In x Ga 1-x Bandgap width of the N absorption layer at the V-pit platform.

[0015] Optional, In x Ga 1-x The In component of the N absorption layer at the sidewall of the V pit is smaller than that of the In x Ga 1-x In composition of the N absorption layer at the V-pit platform.

[0016] Optional, In x Ga 1-x The thickness of the N absorption layer at the side wall of the V pit is smaller than that of the In x Ga 1-x The thickness of the N absorption layer at the V-pit platform.

[0017] Compared with the prior art, the InGaN-based visible light detector provided by the present invention is a method for sequentially growing a GaN cap layer and an Al y Ga 1-y N cap layer to protect In x Ga 1-x N absorption layer, to avoid the In x Ga 1-x The GaN cap layer is grown at a relatively low temperature to form a physical barrier, which improves the interface quality and isolates the high temperature process from the In absorption layer. x Ga 1-x Destruction of the N absorption layer. Wide bandgap Al y Ga 1-y The N cap layer can form an electron / hole blocking barrier to partially offset the In x Ga 1-x The polarization electric field of the N absorption layer reduces the accumulation of interface charges, achieves the matching of the polarization electric field, and reduces the polarization effect. y Ga 1-y The conduction band offset of the N cap layer can inhibit the electrons from flowing from the n-type layer to the In x Ga 1-x The reverse diffusion of the N absorption layer effectively reduces the dark current of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of the structure of the detector in Example 1 of the present invention.

[0020] Figure 2 Schematic diagram of the flow of photocurrent on the V-pit platform and sidewalls obtained by the detector simulation software Silvaco in Example 1 of the present invention.

[0021] Figure 3 1 is a comparison diagram of the current-voltage characteristic curves of the detectors in Example 1 of the present invention and Comparative Example 1.

[0022] Figure 4 This is a comparison diagram of the energy bands on the V-pit platform obtained by using the simulation software Silvaco for the detectors in Example 1 of the present invention and Comparative Example 1.

[0023] Figure 5 Silvaco is a comparison diagram of energy bands on the sidewall of the V-pit obtained by using the simulation software Silvaco for the detectors in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0025] The embodiment of the present application provides an InGaN-based visible light detector, comprising: substrate; an n-type layer located on the substrate; The active layer is located on the n-type layer; the active layer is composed of multiple unit structures stacked periodically, each unit structure includes In high In content grown sequentially x Ga 1-x N absorption layer, cap layer and GaN quantum barrier layer; the cap layer consists of GaN cap layer and Al y Ga 1-y The active layer is composed of an N cap layer; the active layer has a V-pit, which runs through the entire active layer and includes a V-pit sidewall and a V-pit platform; The p-type layer is located on the active layer.

[0026] In the embodiment of the present application, a GaN cap layer and an Al y Ga 1-y N cap layer to protect In x Ga 1-x N absorption layer, reducing the subsequent GaN quantum barrier layer growth temperature rise process and p-type layer high temperature growth of In x Ga 1-xThe damage caused by the N absorption layer. And the wide bandgap AlGaN cap layer can form an electron / hole blocking barrier, partially offsetting the In x Ga 1-x The polarization electric field of the N absorption layer reduces the accumulation of interface charges, achieves matching of the polarization electric field, and reduces the polarization effect. At the same time, the conduction band offset of the AlGaN cap layer can inhibit the electrons from the n-type layer to the In x Ga 1-x Back diffusion of the N absorption layer, which is usually the main source of dark current in the detector. y Ga 1-y The N capping layer can also improve the crystal quality of the material by compensating for strain.

[0027] In some embodiments, x Ga 1-x In the N absorption layer, the value range of x is 0.3 ≤ x ≤ 0.6, and 0.3, 0.4, 0.5, and 0.6 are exemplary, but not limited thereto. x Ga 1-x The function of the N absorption layer is to convert the incident optical signal into an electrical signal and respond to the corresponding wavelength within a range of values.

[0028] In some embodiments, the thickness of the GaN cap layer ranges from 0.5 nm to 1 nm, and is exemplified by 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, and 1 nm, but is not limited thereto. x Ga 1-x A primary barrier is formed on the N absorption layer to protect In x Ga 1-x The N absorption layer initially limits the photogenerated carriers, and the regulation of the polarization electric field is achieved within this thickness range.

[0029] In some embodiments, Al y Ga 1-y The thickness of the N cap layer ranges from 0.5 nm to 2 nm, exemplified by 0.5 nm, 0.8 nm, 1 nm, and 2 nm, but not limited thereto. y Ga 1-y The role of the N cap layer is to alleviate the In x Ga 1-x The piezoelectric polarization generated by the compressive stress in the N absorption layer partially offsets the QCSE within this thickness range, reduces the band tilt, and suppresses electron leakage.

[0030] In some embodiments, Al y Ga 1-yIn the N cap layer, the value range of y is 0.1 ≤ y ≤ 0.4, and 0.1, 0.2, 0.3, and 0.4 are exemplary, but not limited to these. y Ga 1-y The role of the N capping layer is to regulate the height of the electron / hole blocking barrier, reduce the accumulation of interfacial charge, achieve matching of the polarization electric field, and reduce the polarization effect within this value range.

[0031] In some embodiments, x Ga 1-x The band gap width of the N absorption layer at the side wall of the V pit is larger than that of the In x Ga 1-x The band gap width of the N absorption layer at the V-pit platform is reduced, thereby suppressing electron leakage.

[0032] In some embodiments, x Ga 1-x The In component of the N absorption layer at the sidewall of the V pit is smaller than that of the In x Ga 1-x The In component of the N absorption layer at the V-pit platform realizes the energy band regulation at the V-pit.

[0033] In some embodiments, x Ga 1-x The thickness of the N absorption layer at the side wall of the V pit is smaller than that of the In x Ga 1-x The thickness of the N absorption layer at the V-pit platform realizes the regulation of the polarization electric field at the V-pit. Example 1

[0034] This example uses a self-made MOCVD system for epitaxial growth. The substrate used is a Si substrate, and the epitaxial structure is as follows: AlN buffer layer 201, n-GaN layer 301, preparation layer 401, active layer 500, p-type Al z Ga 1-z The active layer 500 is composed of 12 unit structures stacked periodically, each unit structure includes In x Ga 1-x N absorption layer 501, cap layer 510 and GaN quantum barrier layer 504; cap layer 510 is composed of GaN cap layer 502 and Al y Ga 1-y The preparation layer 401 will generate a V pit 801 along the dislocation line 701 during the growth process. The V pit 801 includes a V pit sidewall 802 and a V pit platform 803. The V pit 801 runs through the entire active layer 500 and the p-type Al z Ga 1-zThe N layer 601 and the p-type GaN layer 602 fill the V-pit 801 .

[0035] Among them, x Ga 1-x In the N absorption layer 501, x=0.6, Al y Ga 1-y In the N cap layer 503, y=0.3, p-type Al x Ga 1-x The thickness of the n-type GaN layer 301 is 3 μm, the thickness of the GaN cap layer 502 is 0.6 nm, and the thickness of the Al y Ga 1-y The thickness of the N cap layer 503 is 2 nm.

[0036] The thickness of the preparation layer 401 on the V-pit sidewall 802 is much smaller than that on the V-pit platform 803. x Ga 1-x When the N absorption layer 501 is formed, the V pit continues to grow. x Ga 1-x The thickness and In composition of the N absorption layer 501 at the V-pit sidewall 802 are smaller than those at the V-pit platform 803. x Ga 1-x The band gap of the N absorption layer 501 is larger than that of the In absorption layer at the V-pit platform 803. x Ga 1-x The N absorption layer can suppress the dark current from leaking from the V pit sidewall 802. Due to the existence of the V pit 801, the V pit 801 can also release In x Ga 1-x The stress on the N absorption layer 501. The V pit 801 will x Ga 1-x The N absorption layer 501 is divided into small pieces, which prevents the transfer of stress and x Ga 1-x The long-range stress on the N absorption layer 501 is converted into isolated local stress, so that the stress on the InGaN absorption layer 501 is reduced.

[0037] In x Ga 1-x After the growth of the N absorption layer 501 is completed, a GaN cap layer 502 is quickly grown while maintaining the growth temperature constant, and then the Al y Ga 1-y N cap layer 503 protects the grown In x Ga 1-x N absorption layer 501, reducing the subsequent temperature rise process of the GaN quantum barrier layer 504 growth and the p-type Al z Ga 1-zThe high temperature growth of the N layer 601 and the p-type GaN layer 602 has a great influence on the growth of the In x Ga 1-x Damage caused by the N absorption layer 501. Wide bandgap Al y Ga 1-y The N cap layer 503 can form an electron / hole blocking barrier to partially offset the In x Ga 1-x The polarization electric field of the N absorption layer 501 reduces the accumulation of interface charges, achieves polarization electric field matching, and reduces the polarization effect. y Ga 1-y The conduction band offset of the N cap layer 503 can inhibit the electrons from flowing from the n-type GaN layer 301 to the In x Ga 1-x Back diffusion of the N absorption layer 501 is usually the main source of the detector dark current. y Ga 1-y The N cap layer 503 can also improve the crystal quality of the material by compensating for strain, and provide a suitable channel for the separation and transport of photogenerated carriers in the depletion layer.

[0038] Figure 2 This is a schematic diagram of the flow of photocurrent on the V-pit platform 803 and the V-pit sidewall 802 obtained by using the simulation software Silvalco for the InGaN-based visible light detector prepared in this embodiment. x Ga 1-x Al is grown after the N absorption layer 501 y Ga 1-y N cap layer 503, hole current is In x Ga 1-x After the N absorption layer 501 is generated, it separates into the p-type Al through the V-pit sidewall 802 z Ga 1-z The N layer 601 and the p-type GaN layer 602 transmit, and at the same time, the hole current moves laterally under the electric field, and the addition of Al y Ga 1-y The current behind the N cap layer 503 will not move in other directions. Comparative Example 1

[0039] The structure of the InGaN-based visible light detector provided in Comparative Example 1 is substantially the same as that of Example 1, except that the unit structure of the active layer 500 does not include the cap layer 510. x Ga 1-x A GaN quantum barrier layer 504 is grown on the N absorption layer 501 .

[0040] Comparing the current-voltage characteristic curve, V-pit platform energy band diagram and V-pit sidewall energy band diagram of the InGaN-based visible light detector provided in Example 1 and Comparative Example 1, respectively, Figure 3 、 4 , as shown in 5.

[0041] from Figure 3 It can be seen from the figure that under reverse voltage, the dark current of the visible light detector in Example 1 is smaller. Compared with the visible light detector in Comparative Example 1, the dark current is 2 orders of magnitude lower on average, and can reach 10 at a reverse voltage of -5 V. -10 Order of magnitude.

[0042] from Figure 4 It can be seen that the band gap width of the visible light detector provided by Example 1 and Comparative Example 1 in the active layer of the V-pit platform 803 is basically the same, and the potential barrier of the cap layer 510 in the active layer region of the V-pit platform 803 is higher. y Ga 1-y The conduction band of the N cap layer 503 is further raised, forming a stronger electron blocking layer, which inhibits electrons from x Ga 1-x The N absorption layer 501 leaks toward the p-type layer.

[0043] from Figure 5 It can be seen that the bandgap widths of the active layer of the V-pit sidewall 802 of the visible light detector provided by Example 1 and Comparative Example 1 are very different. It can be seen that the cover layer 510 has a great influence on the bandgap width of the active layer of the detector at the V-pit sidewall 802. y Ga 1-y A sudden change occurs in the conduction band and the valence band at the interface between the N cap layer 503 and the GaN quantum barrier layer 504, forming an additional potential barrier to further confine the carriers.

[0044] from Figure 4 and Figure 5 It can be found that the cap layer 510 has a more significant effect on the V-pit sidewall 802. y Ga 1-y The conduction band offset of the N cap layer 503 can inhibit the electrons from flowing from the n-type GaN layer 301 to the In x Ga 1-x The reverse diffusion of the N absorption layer 501 and the formation of a stronger electron blocking layer inhibit the electrons from x Ga 1-x The N absorption layer 501 leaks into the p-type layer, thereby reducing the dark current of the detector.

Claims

1. An InGaN-based visible light detector, characterized in that: include: substrate; an n-type layer located on the substrate; an active layer located on the n-type layer; The active layer is composed of a plurality of unit structures stacked periodically, each unit structure includes In x Ga 1-x N absorption layer, cap layer and GaN quantum barrier layer; the cap layer is composed of GaN cap layer and Al y Ga 1-y The active layer is composed of an N cap layer; the active layer has a V-pit, which runs through the entire active layer and includes a V-pit sidewall and a V-pit platform; The p-type layer is located on the active layer.

2. The InGaN-based visible light detector according to claim 1, wherein: In x Ga 1-x In the N absorption layer, the value range of x is 0.3 ≤ x ≤ 0.

6.

3. The InGaN-based visible light detector according to claim 1, wherein: The thickness of the GaN cap layer ranges from 0.5 nm to 1 nm, inclusive.

4. The InGaN-based visible light detector according to claim 1, wherein: The Al y Ga 1-y The thickness of the N cap layer ranges from 0.5 nm to 2 nm, inclusive.

5. The InGaN-based visible light detector according to claim 1, characterized in that: The Al y Ga 1-y In the N cap layer, the value range of y is 0.1 ≤ y ≤ 0.

4.

6. The InGaN-based visible light detector according to claim 1, characterized in that: In x Ga 1-x The band gap width of the N absorption layer at the side wall of the V pit is larger than that of the In x Ga 1-x Bandgap width of the N absorption layer at the V-pit platform.

7. The InGaN-based visible light detector according to claim 1, characterized in that: In x Ga 1-x The In component of the N absorption layer at the sidewall of the V pit is smaller than that of the In x Ga 1-x In composition of the N absorption layer at the V-pit platform.

8. The InGaN-based visible light detector according to claim 1, characterized in that: In x Ga 1-x The thickness of the N absorption layer at the side wall of the V pit is smaller than that of the In x Ga 1-x The thickness of the N absorption layer at the V-pit platform.

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