Room temperature uncooled infrared photoelectric detector based on InGaAs triangular barrier structure

Abstract

The invention relates to the field of infrared photoelectric detector research, in particular to a room-temperature uncooled infrared photoelectric detector based on an InGaAs triangular barrier structure. The semiconductor device sequentially comprises a substrate, an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a delta-p-type doped III-V compound semiconductor layer, an i-type semiconductor layer and an n-type doped III-V compound semiconductor layer from bottom to top, wherein the n-type doped III-V compound semiconductor layer is provided with an electrode; the problems that a traditional semiconductor type photoelectric detector is large in background noise and low in sensitivity due to the fact that the traditional semiconductor type photoelectric detector is influenced by the room temperature can be solved, and infrared detection of the room temperature is achieved.

Description

Technical Field

[0001] The invention relates to the research field of infrared photoelectric detectors, and in particular to a room temperature non-cooled infrared photoelectric detector based on an InGaAs triangular barrier structure. Background Art

[0002] Infrared photoelectric detectors are widely used in astronomy (star imaging in the infrared band), communications (fiber optic communications), military (night vision imaging), etc. Current infrared photoelectric detectors can be divided into two categories based on the detection principle: semiconductor infrared detectors based on the photoelectric effect and thermal infrared detectors based on the infrared photothermal effect.

[0003] Semiconductor detectors based on the photoelectric effect have the advantages of high sensitivity, fast response speed, easy miniaturization, sensitivity to wavelength, and easy pixelation. They are widely used in aerospace, missile guidance, infrared night vision and other fields with high requirements on dynamic response speed, sensitivity, anti-interference and imaging quality. However, since their signal-to-noise ratio is easily affected by temperature, they need to work at low temperatures, so they need to be equipped with refrigeration equipment; thermistor detectors based on the infrared photothermal effect use the characteristic that the temperature of the sensitive element rises after absorbing infrared light, so they have the characteristics of slow response speed, wide temperature spectrum, low sensitivity, etc., but they do not require a refrigeration system, so the cost is lower.

[0004] The working principle of semiconductor photodetectors is that when incident light irradiates semiconductor materials, when the photon energy is greater than the bandgap width, the photon energy is absorbed by the semiconductor, causing the valence band electrons in the semiconductor to transition to the conduction band, forming photogenerated electrons and photogenerated holes. Since the absorption of photons by semiconductors must satisfy the requirement that the photon energy is greater than the semiconductor bandgap width, the semiconductor materials used for infrared detection must have a smaller bandgap width, such as narrow bandgap semiconductor materials such as PbS, HgCdTe, PbSnTe, InGaAs, InSb, and GaSb. In order to enable photogenerated electrons to generate open-circuit voltage or form external circuit current for detection, semiconductor infrared sensors are constructed as PN or PIN structures, such as Figure 1 and Figure 2 shown.

[0005] For the PIN structure, an intrinsic I layer is added between the P-type layer and the N-type layer, which widens the width of the depletion layer under bias, increases the absorption efficiency of photons and suppresses the recombination of photogenerated electrons and holes.

[0006] In order to further improve the external quantum efficiency of infrared photodetectors, infrared detectors with semiconductor heterojunction structures have also been designed, such as Figure 3As shown. In this band structure, the band steps of the P layer and the I layer are on the conduction band side, while the band steps of the N layer and the I layer are on the valence band side. Therefore, neither the photogenerated electrons nor the holes will be hindered by the potential barrier, thereby avoiding the loss of photogenerated carriers at the interface, and can effectively suppress the recombination of photogenerated carriers and improve the separation efficiency. Another advantage of this structure is that it can reduce the interference of the forward diffusion current on the output signal. Since the P layer introduces a potential barrier in the conduction band, it hinders the injection of electrons from the I layer to the P layer caused by the diffusion movement. Similarly, the injection of holes into the N layer is also suppressed, so the impact of the forward diffusion current on the device output can be effectively reduced. For devices with this structure, when selecting the P layer and N layer materials, the band gap width and electron affinity of the materials should be comprehensively considered for screening, and the conditions of this "step-type" band structure should be met as much as possible. For the P layer material, the electron affinity should be as small as possible, and the band gap width should not be too large to avoid the P layer material introducing a large band step in the valence band. For the N-layer material, the electron affinity should be close to that of the I-layer material to avoid the N-layer material introducing a large band step in the conduction band. Therefore, the material system that satisfies this structural band structure is very limited, which limits its detection of different infrared wavelengths.

[0007] In order to avoid the selectivity of infrared photon wavelengths due to the material bandgap, quantum well and superlattice structure infrared photodetectors have also been developed. Figure 4 (a) and Figure 4 As shown in (b), superlattice can suppress Auger recombination through band structure design. Its electron effective mass, especially the electron effective mass of long-wave infrared superlattice material, is large, which is conducive to suppressing tunneling current. At the same time, this technology is based on relatively mature III-V compound semiconductor materials, which can obtain good consistency between materials and devices. In addition, the detection wavelength is easy to adjust. By changing the quantum well width and barrier height, responses in different wavelength ranges can be obtained. The spectral response bandwidth is narrow, and the optical crosstalk between different bands is small, which can realize dual-color and multi-color infrared detection.

[0008] However, the semiconductor infrared photodetectors of the above structures are very susceptible to thermal noise, so they need to be equipped with refrigeration equipment and work at low temperatures to achieve a good signal-to-noise ratio. This is because the electrons in the valence band can not only be excited by light to transition to the conduction band, but also by thermal excitation to transition to the conduction band, which leads to a large dark current at room temperature, a small gain of the photoelectric signal, and a poor signal-to-noise ratio. In order to suppress the dark current, the infrared detector needs to work at low temperatures. Summary of the invention

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a room-temperature uncooled infrared photodetector with a triangular barrier structure, which can improve the problems of large background noise and low sensitivity of traditional semiconductor photodetectors caused by the influence of room temperature, and realize infrared detection at room temperature.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention provides a room-temperature uncooled infrared photoelectric detector with a triangular barrier structure, which comprises, from bottom to top, a substrate, an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a δ-p-type doped III-V compound semiconductor layer, an i-type semiconductor layer and an n-type doped III-V compound semiconductor layer; the n-type doped III-V compound semiconductor layer is provided with an electrode.

[0012] Preferably, the substrate is a III-V semiconductor substrate.

[0013] Preferably, the III-V semiconductor substrate is an InP substrate.

[0014] Preferably, the δ-p type doped III-V compound semiconductor layer is an InGaAs layer, and the p-type doped element is Mg.

[0015] Preferably, the n-type doped III-V compound semiconductor layer is an InGaAs layer.

[0016] Preferably, the i-type semiconductor layer is an InGaAs layer.

[0017] Preferably, the bandgap width of the InGaAs layer is 0.8 eV.

[0018] Preferably, the height of the triangular barrier structure of the detector is 0.7 eV.

[0019] Preferably, the thickness of the δ-p type doped III-V compound semiconductor layer is

[0020] Preferably, the n-type doped III-V compound semiconductor layer has a thickness of micrometer order.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention establishes a triangular barrier energy band structure through an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a δ-p-type doped III-V compound semiconductor layer, an i-type semiconductor layer and an n-type doped III-V compound semiconductor layer. The present invention transforms the traditional photocurrent response caused by photogenerated carriers into photon injection to adjust the barrier height to indirectly achieve the photocurrent response, which can improve the problem of large background noise and low sensitivity caused by the influence of room temperature on the traditional semiconductor photodetector. At the same time, the present invention converts the light response into the change of the triangular barrier height, and the current has an exponential relationship with the barrier height, and the accumulation of thermally excited carriers at the barrier in a dark environment does not affect the reduction of the barrier height caused by subsequent photogenerated carriers, which can effectively improve the switching ratio and sensitivity of the photodetector and realize infrared detection at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the process of PN junction absorbing infrared light and converting it into electrical signals;

[0024] Figure 2 Schematic diagram of the process of PIN junction absorbing infrared light and converting it into electrical signals;

[0025] Figure 3 An infrared photodetector having a heterojunction structure with an electron barrier and a hole barrier;

[0026] Figure 4 (a) is a schematic diagram of a superlattice;

[0027] Figure 4 (b) is a schematic diagram of the quantum well structure;

[0028] Figure 5 Schematic diagram of the epitaxial structure of the triangular barrier infrared photodetector of the present invention;

[0029] Figure 6 Schematic diagram of the energy band structure of the triangular barrier infrared photodetector of the present invention;

[0030] Figure 7 A schematic diagram of the change in potential barrier height of the triangular potential barrier infrared photoelectric detector of the present invention before and after illumination;

[0031] Figure 8 It is a schematic diagram of the variation curve of the photocurrent and dark current of the triangular barrier infrared photodetector of the present invention with respect to the bias voltage;

[0032] Fig. 9 It is a schematic diagram of the structure of the triangular barrier epitaxial wafer of the present invention;

[0033] Fig.10 Schematic diagram of the triangular barrier energy band structure of the present invention;

[0034] Fig.11 A top view of the triangular barrier infrared photodetector of the present invention;

[0035] Fig.12 This is a data diagram of the infrared detection performance of the triangular barrier infrared photoelectric detector of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0038] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0039] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0040] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0042] The present invention is based on III-V compound semiconductors and provides a room temperature non-cooled infrared photodetector with a triangular barrier structure, which includes a substrate, an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a δ-p-type doped III-V compound semiconductor layer, an i-type semiconductor layer and an n-type doped III-V compound semiconductor layer from bottom to top, and the n-type doped III-V compound semiconductor layer is provided with electrodes. The semiconductor growth structure of nipin forms a band structure of a triangular barrier, which can realize infrared photodetection. The substrate serves as a supporting structure of the detector and provides a stable mechanical basis for the entire device. The n-type doped III-V compound semiconductor layer serves as the starting conductive layer of the detector, provides free electrons through n-type doping, and participates in the conductive process. At the same time, the layer also serves as an incident layer of infrared radiation, receiving and absorbing infrared radiation. The i-type semiconductor layer serves as an intrinsic layer, and its conductivity is between that of the n-type doped III-V compound semiconductor layer and the δ-p-type doped III-V compound semiconductor layer. The i-type semiconductor layer mainly plays a transition and buffering role, which helps to reduce the lattice mismatch and stress at the interface and improve the stability and performance of the device. The δ-p-type doped III-V compound semiconductor layer provides holes through p-type doping to form a pn junction with the n-type layer. Under the action of infrared radiation, the holes in this layer recombine with the free electrons in the n-type layer to generate photocurrent.

[0043] The present invention epitaxially grows an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a p-type doped compound semiconductor layer, an i-type semiconductor layer, and an n-type doped III-V compound semiconductor layer on a III-V semiconductor substrate to form a semiconductor substrate having the following characteristics: Figure 5 The epitaxial structure and Figure 6 Device with the band structure shown.

[0044] When infrared light with photon energy greater than the bandgap width is incident, holes migrate to the p-type doped compound semiconductor layer within the valence band and gather in the p-type doped compound semiconductor layer, resulting in a decrease in the barrier height. When a bias voltage is applied to the device, the current density has an exponential inverse relationship with the barrier height, as shown in formula (1):

[0045]

[0046] Therefore, the device will produce significant photocurrent gain. Where A is the proportionality coefficient, T is the temperature, q is the carrier charge, φ0 is the barrier height, V B is the bias voltage, and k is the Boltzmann constant.

[0047] like Figure 7As shown in the figure, when a bias voltage of VB is applied under dark conditions, the dark current is very small because electrons have to pass through a potential barrier with a height of φ0 to form a current; under light conditions, when the incident photon energy is greater than the bandgap width, photogenerated electrons and photogenerated holes will be generated in the conduction band EC and the valence band EV respectively. The photogenerated holes will move to the p-layer, that is, the potential barrier layer, under the built-in electric field formed by doping, and gradually gather. The aggregation of holes will lead to the lowering of the potential barrier, so there will be a significant current gain under light conditions. The ratio of photocurrent to dark current is:

[0048]

[0049] Among them, I light is the photocurrent, I dark is the dark current, φ0 * is the barrier height under illumination conditions, q is the carrier charge, φ0 is the barrier height, k is the Boltzmann constant, and T is the temperature.

[0050] like Figure 8 As shown in the figure, the current gain caused by illumination is proportional to the exponential change of the barrier height. The change of the barrier height depends on the concentration of photogenerated holes, that is, it is proportional to the external quantum efficiency and the light intensity. When the light intensity increases, the concentration of photogenerated holes increases, the change in the barrier height becomes larger, and thus the photocurrent increases exponentially.

[0051] The substrate is a III-V semiconductor substrate, and the III-V semiconductor substrate is an InP substrate. The InP substrate has good lattice matching with the n-type doped III-V compound semiconductor layer, and the n-type doped III-V compound semiconductor layer grown on the InP substrate can have a lower defect density and higher crystal quality, which helps to improve the performance and stability of the detector. The InP material has a higher thermal conductivity, which helps the detector to effectively dissipate heat during operation, prevents performance degradation or failure due to overheating, and ensures the reliability of the detector under long-term, high-power density working conditions.

[0052] The δ-p type doped III-V compound semiconductor layer, the n-type doped III-V compound semiconductor layer and the i-type semiconductor layer are all InGaAs layers, which can ensure the material consistency between the layers inside the detector, help reduce the lattice mismatch and stress at the interface, reduce the defect density, and thus improve the crystal quality and overall performance of the detector. Secondly, the InGaAs material has an adjustable band structure, and the spectral response range of the detector can be optimized by adjusting the component ratio of In and Ga. Especially in the infrared band, InGaAs exhibits good absorption characteristics, allowing the detector to efficiently receive and convert infrared radiation into electrical signals. In addition, the InGaAs material has a lower dark current density, which helps to reduce the noise level of the detector and improve the signal-to-noise ratio. Especially under low light conditions, low dark current is crucial to ensure the sensitivity and accuracy of the detector.

[0053] The p-type doping element is Mg, which can effectively introduce holes into the InGaAs layer to form a stable p-type conductive channel. The Mg-doped p-type InGaAs layer combined with the n-type InGaAs layer can form a high-quality pn junction, which helps to improve the photoelectric conversion efficiency and response speed of the detector.

[0054] The bandgap width of the InGaAs layer is 0.8 eV, corresponding to a wavelength of about 1.55 μm (according to the photon energy formula E=hν=hc / λ, where E is the photon energy, h is the Planck constant, ν is the photon frequency, λ is the wavelength, and c is the speed of light). The detector has good spectral response characteristics in the infrared band, especially in the near-infrared and mid-infrared regions. By adjusting the composition ratio of In and Ga, the bandgap width of the InGaAs layer can be further fine-tuned to optimize the spectral response range of the detector so that it better matches the wavelength of the target infrared radiation.

[0055] The triangular barrier structure height of the detector is 0.7eV, which forms an effective electric field inside the detector, which helps separate photogenerated carriers (electrons and holes) and migrate to their respective electrodes. A higher barrier height can more effectively prevent the recombination of carriers, thereby improving the photoelectric conversion efficiency of the detector. At the same time, the electric field also helps to reduce the dark current of the detector and improve the signal-to-noise ratio. Due to the reasonable matching of the bandgap width of the InGaAs layer and the height of the triangular barrier structure, the detector can more effectively absorb and convert infrared radiation into electrical signals, which helps to improve the quantum efficiency of the detector, that is, the probability of each incident photon generating a photoelectron. This enables the detector to capture more infrared radiation energy, thereby improving its sensitivity and response speed.

[0056] In addition, the thickness of the δ-p type doped III-V compound semiconductor layer is The thickness of the n-type doped III-V compound semiconductor layer is in the micrometer level.

[0057] Fig. 9 It is a schematic diagram of the structure of the triangular barrier epitaxial wafer of the present invention; Fig.10 The schematic diagram of the triangular barrier energy band structure of the present invention is shown in FIG. 1 . The present invention can control the sensitive wavelength of the sensor by adjusting the ratio of In / Ga. 0.5 Ga 0.5 Taking the As component as an example, its sensitive wavelength is <1500nm (the test used 1300nm infrared). When the In component is increased, the wavelength moves toward the long-wave direction; when the Ga component is increased, the wavelength moves toward the short-wave direction. 0.5 Ga 0.5 The bandgap width of As is about 0.8eV, and the height of the triangular barrier of the homojunction constructed by doping is about 0.7eV. The device is insulated and isolated by etching, such as Fig.11 As shown, the size of a single device is 50μm, the size of the photosensitive area is 30μm, and the detection performance of infrared light with a wavelength of 1300nm is as follows Fig.12 shown.

[0058] In summary, the present invention provides an infrared light sensor with a new energy band structure (triangular potential barrier), which can realize non-cooled infrared detection at room temperature, and has higher photocurrent gain and photoelectric response than other existing infrared sensors. The present invention transforms the traditional photocurrent response based on photogenerated carriers into indirectly realizing photocurrent response by adjusting the barrier height by photon injection. This new structure and photocurrent response mechanism can improve the problem of large background noise and low sensitivity caused by the influence of room temperature on traditional semiconductor photodetectors. The photocurrent intensity of the traditional diode-structured infrared photodetector is proportional to the concentration of photogenerated carriers, that is, proportional to the light intensity. Under dark conditions, due to the small bandgap width of the semiconductor material used in the infrared photodetector, thermally excited carriers become the main factor of dark current. Therefore, when the light intensity is weak, the concentration of photogenerated carriers is similar to the concentration of thermally excited carriers, making the switch of the detector relatively small, and infrared detection applications cannot be realized. The present invention converts the illumination response into a change in the height of a triangular potential barrier, and the current has an exponential relationship with the potential barrier height. In addition, the accumulation of thermally excited carriers at the potential barrier in a dark environment does not affect the reduction in the potential barrier height caused by subsequent photogenerated carriers. This can effectively improve the switching ratio and sensitivity of the photodetector and realize infrared detection at room temperature.

[0059] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A room temperature uncooled infrared photodetector with a triangular barrier structure, characterized in that: From bottom to top, it includes a substrate, an n-type doped III-V compound semiconductor layer, an i-type semiconductor layer, a δ-p-type doped III-V compound semiconductor layer, an i-type semiconductor layer and an n-type doped III-V compound semiconductor layer; each of the n-type doped III-V compound semiconductor layers is provided with an electrode.

2. A room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The substrate is a III-V semiconductor substrate.

3. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 2, characterized in that: The III-V semiconductor substrate is an InP substrate.

4. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The δ-p type doped III-V compound semiconductor layer is an InGaAs layer, and the p-type doped element is Mg.

5. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The n-type doped III-V compound semiconductor layer is an InGaAs layer.

6. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 5, characterized in that: The i-type semiconductor layer is an InGaAs layer.

7. A room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 4 or 6, characterized in that: The bandgap width of the InGaAs layer is 0.8 eV.

8. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The triangular barrier structure height of the detector is 0.7 eV.

9. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The thickness of the δ-p type doped III-V compound semiconductor layer is 10. The room temperature uncooled infrared photodetector with a triangular barrier structure according to claim 1, characterized in that: The thickness of the n-type doped III-V compound semiconductor layer is in the micrometer level.

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