An infrared photodetector with a secondary photoelectric response

Abstract

The present invention discloses an infrared photodetector with a secondary optoelectronic response, which includes an insulating substrate, a gold electrode, a silver electrode, an n-type InSe semiconductor, and a p-type GaSe semiconductor. The structure of the photodetector in this solution is as follows: the gold electrode is above the insulating substrate, the GaSe semiconductor is above the gold electrode, the InSe semiconductor is above the GaSe semiconductor and forms an InSe / GaSe heterojunction, the silver electrode is above the InSe. The InSe / GaSe heterojunction formed by the contact between the InSe semiconductor and the GaSe semiconductor has PN junction characteristics and can form a built-in electric field to effectively suppress the dark current of the detector. The optical second-order nonlinearity of the InSe semiconductor and the GaSe semiconductor converts infrared light that cannot be absorbed by the InSe semiconductor and the GaSe semiconductor into second harmonics that can be absorbed by the InSe semiconductor, thereby generating photo-generated carriers, and further generating photocurrent under the action of the built-in electric field of the PN junction. The detector in this solution has a second-order power coefficient and can be used for ultra-short pulse width measurement, super-resolution imaging, and ultrafast optoelectronic mixing signal processing.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection, and particularly relates to an infrared optoelectronic detector with a secondary optoelectronic response. Background Art

[0002] Optoelectronic detectors, by converting optical signals into electrical signals, have important applications in modern society. The photocurrent response (I ph ) of these detectors has a corresponding relationship with the power (P): the photocurrent I ph ∝ P α , where α is the corresponding power coefficient. Depending on the value of α, the application scenarios of the detectors are also different; for applications that require determining the responsivity R = I ph / P, the value of α should be constantly 1. For some application scenarios, such as the pulse width measurement of ultra-short pulses and the optoelectronic mixing of communication signals, α should be greater than 1.

[0003] Currently, in optoelectronic detectors, α is usually less than or equal to 1. For photovoltaic detectors, they usually use the linear absorption of semiconducting materials for photons with energies greater than the bandgap to achieve optoelectronic detection. This principle converts the absorbed photons into electron-hole pairs, which are then separated and collected through the built-in electric field. Its α value is usually 1 and its responsivity usually does not change with power. For detectors based on the photoconductive effect, limited by defect trapping and other non-ideal effects, α is usually less than 1, and its responsivity decreases with the increase in power.

[0004] Currently, infrared optoelectronic detection is mainly achieved by selecting corresponding narrow-bandgap semiconductors. For example, selecting the semiconductor material germanium with a bandgap of 0.66 eV. When the photon energy is greater than 0.66 eV (wavelength less than 1878 nm), the incident light can cause optical absorption inside the material. On this basis, a built-in electric field is constructed to achieve the collection of photo-generated carriers and the suppression of dark current. Due to the small bandgap of the material, it is difficult for such detectors to suppress dark current. At the same time, due to the use of linear optical absorption, the power dependence coefficient of such detectors can only be less than or equal to 1. When the bandgap is greater than the photon energy, sub-bandgap optoelectronic detection can be achieved through non-linear optical effects. Two-photon detection is widely used to achieve sub-bandgap optoelectronic detection. In this effect, two photons are simultaneously absorbed to generate a pair of electron-hole pairs, and its corresponding power coefficient is 2. However, this effect is a third-order non-linear effect, resulting in very low efficiency. Summary of the Invention

[0005] Aiming at the above deficiencies of the prior art, the present invention provides an infrared optoelectronic detector with a secondary optoelectronic response, which solves the problem that existing optoelectronic detectors cannot achieve efficient infrared detection with a constant power coefficient α value of 2.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] Provided is an infrared photodetector with a second-order photoelectric response, including an insulating substrate, a gold electrode, a silver electrode, an n-type InSe semiconductor, and a p-type GaSe semiconductor. The n-type InSe semiconductor and the p-type GaSe semiconductor are in contact with each other, and a PN junction is formed at the contact part and is located above the gold electrode. The p-type GaSe semiconductor is in contact with the gold electrode, and the silver electrode is in contact with the n-type InSe semiconductor. A negative voltage is applied to the gold electrode, and a positive voltage is applied to the silver electrode. The crystal types of the p-type GaSe semiconductor and the n-type InSe semiconductor are of the ε type with second-order nonlinearity.

[0008] The beneficial effects of adopting the above technical solution are as follows: The working area of the photodetector in this solution is the PN region above the gold electrode, and the built-in electric field in this PN can effectively suppress the dark current. When an infrared pulsed light irradiates the heterojunction region, since both the p-type GaSe semiconductor and the n-type InSe semiconductor are semiconductor materials with extremely strong second-order nonlinear effects, second harmonics will be generated. These second harmonics convert low-energy infrared photons into high-energy photons with twice the energy, which can then be absorbed by the n-type InSe semiconductor to generate a photoelectric response. Since the relationship between the conversion of the second harmonics and the power is a quadratic relationship, the generated photoelectric response has a second-order power coefficient, i.e., α = 2. Since the second harmonics are second-order nonlinear effects, their efficiency is much greater than that of the third-order nonlinear effect two-photon absorption, thus enabling more efficient infrared detection. At the same time, since the second harmonics are coherent nonlinear effects and their conversion time is on the femtosecond scale, they have the potential for high-speed detection.

[0009] Further, the thickness range of the p-type GaSe semiconductor is [50 nm, 100 nm]; this range can ensure that the second-order nonlinear effect of the p-type GaSe semiconductor is strong enough, while avoiding excessive series resistance caused by the low mobility of the p-type GaSe semiconductor.

[0010] Further, the thickness range of the n-type InSe semiconductor is [100 nm, 200 nm]; this range ensures the second-harmonic conversion efficiency of the n-type InSe semiconductor, and at the same time, within this thickness range, the n-type InSe semiconductor can have good electrical conductivity and reduce the series resistance.

[0011] Further, the thickness range of the gold electrode is [25 nm, 50 nm], and the thickness range of the silver electrode is [30 nm, 100 nm].

[0012] Further, the area of the heterojunction region formed between the p-type GaSe semiconductor and the n-type InSe semiconductor above the gold electrode is not less than 5 μm × 5 μm.

[0013] Further, the distance between the silver electrode and the gold electrode ranges from [1 μm, 5 μm]; effectively avoiding the short - circuit of the positive and negative electrodes and simultaneously avoiding excessive series resistance.

[0014] Further, the substrate is an insulating substrate made of sapphire, silicon dioxide, silicon nitride or alumina.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The p - type GaSe semiconductor and the n - type InSe semiconductor have extremely strong second - order optical nonlinearity. Infrared light with a wavelength less than the bandgap of the p - type GaSe semiconductor and the n - type InSe semiconductor, such as photons with an infrared wavelength of 1500 nm, can be converted into photons with a wavelength of 750 nm through the second - harmonic generation effect, and thus can be absorbed by the n - type InSe semiconductor to generate photocurrent. Since the coefficient of the second - harmonic generation with respect to power is 2, the photocurrent generated by the PN junction absorbing the second - harmonic generation is also proportional to the square of the incident light power. At the same time, the detection band of the detector is broadened from 900 nm to 1750 nm.

[0017] 2. The p - type GaSe semiconductor is located above the gold electrode, and electrons mainly conduct vertically in it, shortening the transmission distance and effectively reducing the series resistance in the p - type GaSe semiconductor.

[0018] 3. A PN junction is formed between the p - type GaSe semiconductor and the n - type InSe semiconductor. Its built - in electric field can effectively suppress the dark current, and the dark current value is less than 10 pA. At the same time, the efficient built - in electric field is also beneficial to improving the collection and separation of photo - generated carriers.

[0019] 4. The infrared photodetector of this scheme has a constant second - order power coefficient when detecting infrared, and can be used in applications such as autocorrelation testing of ultrashort pulses, super - resolution imaging, and optoelectronic mixing of signals. Brief Description of the Drawings

[0020] Figure 1 It is a side cross - sectional view of the infrared photodetector of this scheme.

[0021] Figure 2 It is a top view of the infrared photodetector of this scheme.

[0022] Figure 3 It is a graph showing the relationship between the output current and the bias voltage of the infrared photodetector of this scheme under 1500 - nm pulsed light irradiation and in the absence of light.

[0023] Figure 4 It is a graph showing the generation of the second - harmonic generation and the relationship between the corresponding photocurrent and power of the infrared photodetector of this scheme under 1500 - nm pulsed light irradiation.

[0024] Among them, 1. Insulating substrate, 2. Gold electrode, 3. Silver electrode, 4. n-type InSe semiconductor, 5. p-type GaSe semiconductor. Detailed implementation manners

[0025] The following describes the detailed implementation manners of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed implementation manners. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0026] As Figure 1 and Figure 2 shown, the infrared photodetector of this solution includes a substrate 1, a gold electrode 2, a silver electrode 3, an n-type InSe semiconductor 4, and a p-type GaSe semiconductor 5; the crystal types of the p-type GaSe semiconductor 5 and the n-type InSe semiconductor 4 are the ε type with extremely strong second-order nonlinearity, and second harmonic generation occurs under the irradiation of infrared pulsed light, and the wavelength is half of the infrared wavelength.

[0027] The p-type GaSe semiconductor 5 is in electrical contact with the top and side surfaces of the gold electrode 2, so that the p-type GaSe semiconductor 5 wraps part of the top and side surfaces of the gold electrode 2 to prevent short circuit. One end of the n-type InSe semiconductor 4 is disposed on the top of the p-type GaSe semiconductor 5 above the gold electrode 2 to form a PN junction, and the other end is located on the substrate 1. The silver electrode 3 is disposed on the top of the n-type InSe semiconductor 4 on the substrate and has no electrical contact with the p-type GaSe semiconductor 5 and the gold electrode 2. The n-type InSe semiconductor 4 has no electrical contact with the gold electrode 2, a negative voltage is applied to the gold electrode 2, and a positive voltage is applied to the silver electrode 3.

[0028] During specific implementation, it is preferred to use a silicon wafer with a 300 nm thick SiO 2 oxide layer as the insulating substrate 1, the thickness of the silicon is 500 μm, the thickness of the gold electrode 2 is 25 nm, the thickness of the silver electrode 3 is 40 nm, and both the p-type GaSe semiconductor and the n-type InSe semiconductor 4 are layered structures with uniform thickness and form a stepped structure by folding configuration at the edge of the gold electrode. Among them, the thickness of the p-type GaSe semiconductor 5 is 40 nm, and the thickness of the n-type InSe semiconductor 4 is 60 nm.

[0029] As Figure 2As shown, the horizontal length and vertical width of the p-type GaSe semiconductor 5 in a top view are 40 μm and 25 μm respectively, the horizontal length and vertical width of the n-type InSe semiconductor 4 in a top view are 45 μm and 14 μm respectively, the vertical width of the silver electrode 3 is greater than 14 μm, and the area of ​​the top of the n-type InSe semiconductor 4 covered by the silver electrode 3 is 14 μm*14 μm, the p-type GaSe semiconductor 5 is located above the gold electrode 2, and the distance between the silver electrode 3 and the gold electrode 2 is 1-5 μm, the working area of ​​the photodetector is the overlapping area of ​​the p-type GaSe semiconductor 5 and the n-type InSe semiconductor 4 located above the gold electrode 2, and the area of ​​the heterojunction area is not less than 25 μm 2 .

[0030] like Figure 3 As shown in the figure, the output characteristic curve of the infrared photodetector of this scheme is when there is 1500nm pulse light illumination and no illumination in the working area. Under the negative bias working condition, the built-in electric field in the photodetector effectively suppresses the dark current, and its dark current is less than 10pA. At the same time, under the illumination of 1500nm pulse light, the detector produces a significant photoelectric response, and its light-dark current switching ratio is greater than four orders of magnitude.

[0031] like Figure 4 As shown, the PN junction region formed by the p-type GaSe semiconductor 5 and the n-type InSe semiconductor 4 located above the gold electrode 2 of the infrared photodetector of this scheme under different powers generates the second harmonic (curve with circles) and the corresponding photocurrent (curve with triangles) under the illumination of 1500nm pulse light. Since the p-type GaSe semiconductor 5 and the n-type InSe semiconductor 4 are both semiconductor materials with extremely strong optical second-order nonlinear effects, they will generate second harmonics, the wavelength of which is half the wavelength of the infrared pulse light, so low-energy infrared photons can be converted into high-energy photons. Figure 4 It can be seen that the photodetector can efficiently convert 1500nm pulse light into second harmonic, and the coefficient of the second harmonic to power is 2.1. Therefore, the coefficient of the photocurrent and power generated by the detector absorbing the second harmonic is 2.0.

Claims

1. An infrared photodetector with a second-order photoelectric response, characterized in that, it includes an insulating substrate (1), a gold electrode (2), a silver electrode (3), an n-type InSe semiconductor (4), and a p-type GaSe semiconductor (5); the n-type InSe semiconductor (4) and the p-type GaSe semiconductor (5) are in contact with each other, and the contact part forms a PN junction and is located above the gold electrode (2). The p-type GaSe semiconductor (5) is in contact with the gold electrode (2), the silver electrode (3) is in contact with the n-type InSe semiconductor (4), a negative voltage is applied to the gold electrode (2), and a positive voltage is applied to the silver electrode (3); the crystal types of the p-type GaSe semiconductor (5) and the n-type InSe semiconductor (4) are of the ε type with second-order nonlinearity, and second harmonic generation occurs under the irradiation of pulsed light, and infrared light photons with energies less than the band gaps of the p-type GaSe semiconductor (5) and the n-type InSe semiconductor (4) are converted into photons that can be absorbed by the n-type InSe semiconductor (4). These photons are received by the PN junction and converted into photocurrent.

2. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the thickness range of the p-type GaSe semiconductor (5) is [50 nm, 100 nm].

3. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the thickness range of the n-type InSe semiconductor (4) is [50 nm, 200 nm].

4. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the thickness range of the gold electrode (2) is [25 nm, 50 nm].

5. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the thickness range of the silver electrode (3) is [30 nm, 100 nm].

6. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the area of the heterojunction region formed by the overlap between the p-type GaSe semiconductor (5) and the n-type InSe semiconductor (4) located above the gold electrode (2) is not less than 5 μm × 5 μm.

7. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the distance range between the silver electrode (3) and the gold electrode (2) is [1 μm, 5 μm].

8. The infrared photodetector with a second-order photoelectric response according to claim 1, characterized in that, the insulating substrate (1) is an insulating substrate made of sapphire, silicon dioxide, silicon nitride, or aluminum oxide.

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