Doping-dependent photocurrent bipolar response photoelectric detector

Abstract

The invention designs a doping concentration dependent photocurrent bipolar response self-powered photoelectric detector. The photoelectric detector is formed by coupling a pn junction and a Schottky junction back to back. A PN junction is constructed by using oxide semiconductor films with different doping concentrations and different doping concentration gradients and silicon, Schottky junction contact is formed at the bottom of the silicon, and a PN-Schottky junction structure is constructed. When light with different powers enters from the top of the PN junction, the number of photons irradiated into the Schottky junction is different, the direction of a generated light current signal is reversed along with the power density of the incident light, and light current bipolar response and a determined light current inflection point are displayed. The semiconductor films with different doping concentrations or doping concentration gradients have different absorption coefficients for light waves with different wavelengths, so that the inflection point position of bipolar photocurrent response is regulated and controlled. The detector has the advantages of simple manufacturing process and environment-friendly device, and has a wide application prospect in the design aspect of a novel imaging unit.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detection, and relates to a bipolar response photoelectric detector coupled with a PN junction and a Schottky junction, and in particular to a photocurrent bipolar response photoelectric detector dependent on semiconductor film doping concentration and concentration gradient. Background Art

[0002] As an important component of optoelectronic integrated chips, photodetectors have important research significance in the field of modern science and technology. Based on the actual needs of optical encryption communications, filterless systems, high-resolution imaging and other application fields, bipolar photodetectors with reversible current signal polarity have emerged. Bipolar photodetectors provide a new control dimension of photocurrent polarity for the photoelectric conversion process. They can modulate and output bipolar photocurrent signals according to characteristic parameters such as the power density, wavelength, and polarization of the incident light, reflecting multiple information in the process of interaction between the incident light and the semiconductor material, and have important research value.

[0003] In order to realize the design of bipolar photodetectors that respond to photocurrent, researchers have proposed solutions for different scenarios around various light-matter interaction processes. Based on the hydrogen and oxygen evolution processes of P and N-type GaN materials under ultraviolet light of different wavelengths, researchers proposed ultraviolet photocurrent-responsive bipolar photodetectors that can be used for marine communications; based on a back-to-back structure constructed by coupling built-in electric fields in two different directions, researchers used the principle that the penetration depth of incident light of different wavelengths is different to design and prepare bipolar photodetectors that reverse the photocurrent signal in the visible light band with a longer wavelength. However, the photocurrent inflection point of the above-mentioned bipolar photodetectors that respond to photocurrent is usually only related to the wavelength. Due to the physical and chemical properties of the material itself, the position of the inflection point is usually fixed and lacks flexibility, which limits its application in the imaging field. Based on the principle that semiconductor doping technology can change the absorption coefficient of the material, combined with the dual junction region coupling scheme, the flexible modulation of the inflection point of the bipolar photodetector that responds to photocurrent can be achieved through doping regulation. Summary of the invention

[0004] The purpose of the present invention is to realize a doping-dependent photocurrent bipolar response photodetector through a back-to-back coupling structure of a PN junction and a Schottky junction. The present invention provides a method for regulating the position of the inflection point of the photocurrent bipolar response of a photodetector by changing the doping concentration and concentration gradient of a semiconductor film.

[0005] The present invention discloses a photodetector with a doping-dependent photocurrent bipolar response. It is characterized in that: the photodetector comprises a Mn-uniformly doped N-type ZnO film, a P-type Si substrate, an Al film and an ITO transparent electrode; the P-type Si is an intermediate layer, the front side of Si forms a PN junction with the N-type Mn-doped ZnO film of a scale of hundreds of nanometers, and the back side of Si forms a Schottky contact with the Al film of tens of nanometers thick at the bottom. The PN junction and the Schottky junction have built-in electric fields in opposite directions. The ITO film on the top of the Mn-doped ZnO film and the Al film at the bottom are used as electrodes to connect to an external circuit for photocurrent output. The chemical formula of the Mn-doped ZnO film is Zn 1-x Mn x O. When a beam of monochromatic light is incident from the PN junction, as the incident light power density gradually increases, the number of photons that penetrate the PN junction and enter the Schottky junction increases, and the direction of the photocurrent in the external circuit gradually reverses, achieving a bipolar photocurrent response output. The power density inflection point is related to the wavelength of the incident light. The longer the wavelength of the monochromatic light, the greater its penetration coefficient, and the corresponding power density inflection point moves toward a direction with a smaller power density.

[0006] The power density inflection point is related to the Mn doping concentration and doping concentration gradient in the ZnO semiconductor film constituting the photodetector. Compared with the traditional bipolar photodetector, the present invention has the following advantages:

[0007] 1. The present invention can change the absorption coefficient of the ZnO film by adjusting the doping concentration of the film, thereby adjusting the number of photons incident on the Schottky junction, and further modulating the wavelength or power density of the incident light corresponding to the inflection point position of the photodetector. The doping concentration range is 0.00<x<0.12. As the doping concentration increases, the absorption coefficient of the semiconductor film decreases, the incident monochromatic light is absorbed by the ZnO film in large quantities, and the number of photons incident on the Schottky junction is greatly reduced, causing the inflection point of the photocurrent bipolar response photodetector to move toward a stronger power density. Conversely, as the doping concentration decreases, the absorption coefficient of the semiconductor film increases, and the inflection point of the photocurrent bipolar response photodetector with corresponding parameters moves toward a weaker power density.

[0008] 2. The present invention can change the absorption coefficient of the ZnO film by adjusting the doping concentration gradient of the film, thereby adjusting the number of photons incident on the Schottky junction, and further modulating the wavelength or power density of the incident light corresponding to the inflection point position of the photodetector. The doping concentration range is 0.00<x<0.12. As the direction away from the PN junction interface, the gradient doping device in which the doping concentration x gradually increases in the range of 0.00 to 0.12 is defined as a forward gradient device; as the direction away from the PN junction interface, the gradient doping device in which the doping concentration x gradually decreases in the range of 0.00 to 0.12 is defined as a reverse gradient device. The reverse doped film absorbs the incident light strongly, and the incident light is absorbed by the ZnO film in large quantities, and the number of photons incident on the Schottky junction is greatly reduced, resulting in the inflection point of the photocurrent bipolar response photodetector moving toward a stronger power density. On the contrary, the forward-doped film absorbs the incident light weakly, the number of photons incident on the Schottky junction increases, and the inflection point of the photocurrent bipolar response photodetector with corresponding parameters moves toward a weaker power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is the Al / p-type Si / n-type Zn doping concentration dependent in the present invention 1-x Mn x Schematic diagram of O / ITO bipolar self-powered photodetector.

[0010] Where 1.1 is uniformly doped n-type Zn 1-x Mn x O film, 1.2 is ITO electrode, 1.3 is p-type Si, and 1.4 is Al electrode. Figure 2 is the Al / p-type Si / n-type Zn doping concentration dependent in the present invention 1-x Mn x Schematic diagram of O / ITO bipolar self-powered photodetector.

[0011] Where 1.1 is the n-type Zn doping concentration gradient distribution 1-x Mn x O film, 1.2 is ITO electrode, 1.3 is p-type Si, and 1.4 is Al electrode.

[0012] Figure 3 As described in Example 1, under the same power density of the probe light, the wavelength of the incident light is changed, Al / p-type Si / n-type Zn 0.95 Mn 0.15 Current response characteristics of O / ITO bipolar self-powered photodetector.

[0013] Figure 3As described in Example 2, under the same wavelength of detection light irradiation, the incident light power density is changed, and the Al / p-typeSi / n-type Zn with different doping concentrations are 1-x Mn x Current response characteristics of O / ITO bipolar self-powered photodetector.

[0014] Figure 5 As described in Example 3, under the same wavelength of detection light irradiation, the incident light power density is changed, the reverse doping gradient and the forward doping gradient are

[0015] Al / p-type Si / n-type Zn 1-x Mn x Current response characteristics of O / ITO bipolar self-powered photodetector. The doping concentration of the reverse gradient doped film is selected as 0.12, 0.05, 0.00 in the direction away from the PN junction interface; the doping concentration of the forward gradient doped film is selected as 0.00, 0.05, 0.08 in the direction away from the PN junction interface. DETAILED DESCRIPTION

[0016] The technical details of the present invention are further described below in conjunction with the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the main spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0017] 1. Preparation process of the device of the present invention

[0018] A method for achieving uniform doping of Al / p-Si / n-Zn 1-x Mn x The method of O / ITO photodetector comprises the following steps:

[0019] (1) A P-type Si wafer with a resistivity of 1-20 Ωcm, a thickness of 5 μm, and a crystal plane orientation of (100) was cut into a size of 1.0 cm×1.0 cm, ultrasonically cleaned with anhydrous ethanol and deionized water, and etched in a mixed solution of 0.3 wt% NaOH and 8.0 v% isopropanol for 1 min to serve as a spin coating substrate;

[0020] (2) Weighing (CH3COO)2Zn·2H2O and (CH3COO)2Mn·4H2O according to different molar ratios, dissolving in ethanol solution to obtain a 0.25 M solution, using ethylene glycol and ethanolamine in a volume ratio of 1:1 as stabilizers, stirring for 30-60 minutes, and letting stand for more than 24 hours to obtain precursor solutions of different concentrations;

[0021] (3) Take 70 μL of the precursor solution and drop it on the Si substrate. The spin coating speed and duration are selected as low speed 600 rad / min (5s) and high speed 3000

[0022] rad / min (30s). After spin coating, place it on a heating table at 180°C to evaporate the solvent and form a film. Select the precursor solution with the same doping concentration and repeat the above steps three times to obtain a uniformly doped Zn 1-x Mn x O thin film. The film-formed sample was placed in a tube furnace for annealing, filled with argon gas at a flow rate of 190 sccm and oxygen at a flow rate of 10 sccm, annealed at 500 ° C for 1 hour, and the tube was kept at normal pressure;

[0023] (4) Using magnetron sputtering technology to deposit ITO and Al electrodes on the surface of the annealed film, fill with argon gas, the flow rate is 20-40sccm, the sputtering power is 80-200W, the chamber pressure is 1-5Pa, the sputtering time is 5-15min, and the thickness of the electrode is 100-300nm. 1-x Mn x Preparation of O / ITO devices;

[0024] (5) The device is connected to the circuit by connecting the transparent ITO electrode on the top of the ZnO doped device to the Al electrode on the bottom. Under the condition of no external bias, periodic light is applied to test the inflection point position of the device with different doping concentrations;

[0025] A method of realizing concentration gradient doping of Al / p-Si / n-Zn 1-x Mn x The method of O / ITO photodetector comprises the following steps:

[0026] (1) A P-type Si wafer with a resistivity of 1-20 Ωcm, a thickness of 5 μm, and a crystal plane orientation of (100) was cut into a size of 1.0 cm×1.0 cm, ultrasonically cleaned with anhydrous ethanol and deionized water, and etched in a mixed solution of 0.3 wt% NaOH and 8.0 v% isopropanol for 1 min to serve as a spin coating substrate;

[0027] (2) Weighing (CH3COO)2Zn·2H2O and (CH3COO)2Mn·4H2O according to different molar ratios, dissolving in ethanol solution to obtain a 0.25 M solution, using ethylene glycol and ethanolamine in a volume ratio of 1:1 as stabilizers, stirring for 30-60 minutes, and letting stand for more than 24 hours to obtain precursor solutions of different concentrations;

[0028] (3) Take 70 μL of the precursor solution and drop it on the Si substrate. The spin coating speed and duration are selected as low speed 600 rad / min (5s) and high speed 3000

[0029] rad / min (30s). After spin coating, place it on a heating table at 180°C to evaporate the solvent to form a film. Select the precursor solution with different doping concentrations and repeat the above steps three times to obtain a gradient-doped Zn 1-x Mn x O thin film. The film-formed sample was placed in a tube furnace for annealing, filled with argon gas at a flow rate of 190 sccm and oxygen at a flow rate of 10 sccm, annealed at 500 ° C for 1 hour, and the tube was kept at normal pressure;

[0030] (4) Using magnetron sputtering technology to deposit ITO and Al electrodes on the surface of the annealed film, fill with argon gas, the flow rate is 20-40sccm, the sputtering power is 80-200W, the chamber pressure is 1-5Pa, the sputtering time is 5-15min, and the thickness of the electrode is 100-300nm. 1-x Mn x Preparation of O / ITO devices;

[0031] (5) The device is connected to the circuit by connecting the transparent ITO electrode on the top of the ZnO doped device to the Al electrode on the bottom. Under the condition of no external bias, periodic light is applied to test the inflection point position of the device with different doping gradients.

[0032] Second, the present invention is described in detail with specific embodiments below.

[0033] Example 1

[0034] (1) After etching the P-type Si, three layers of Mn doping (CH 3 COO 2 Zn ethanol solution, preparation of N-type Zn 0.95 Mn 0.15 O film;

[0035] (2) making a mask, and magnetron sputtering an ITO electrode on the surface of the doped ZnO film, and magnetron sputtering an Al electrode on the back of the Si wafer;

[0036] (3) Connect the transparent ITO electrode on the top of the ZnO doped device to the Al electrode on the bottom to connect the device to the circuit. The power density is 0.02 mW cm -2 , 1.0mW cm -2 , 12.27 mW cm -2 The monochromatic laser is used as the tested light source. Three wavelengths of 442nm, 633nm and 785nm are selected for testing. The spot area is 0.2mm -2The current signal is recorded using a low-noise current preamplifier and a data acquisition card. It can be seen that the power density inflection point corresponding to the device is related to the wavelength of the incident light. Under the same power density conditions, the longer the wavelength of the monochromatic light, the smaller the power density required to generate a reverse photocurrent signal.

[0037] Comparative Example 2

[0038] (1) After etching the P-type Si, three layers of Mn doping (CH 3 COO 2 Zn ethanol solution, preparation of N-type Zn 0.90 Mn 0.10 O thin film and Zn 0.95 Mn 0.15 O film;

[0039] (2) making a mask, and magnetron sputtering an ITO electrode on the surface of the doped ZnO film, and magnetron sputtering an Al electrode on the back of the Si wafer;

[0040] (3) Connect the transparent ITO electrode on the top of the ZnO doped device to the Al electrode on the bottom to connect the device to the circuit. The power density is 0.02 mW cm -2 , 0.7 mW cm -2 , 9.1mW cm -2 The 442nm laser is used as the tested light source, and the spot area is 0.2mm -2 The current signal is recorded using a low-noise current preamplifier and a data acquisition card. It can be seen that the devices with two doping concentrations have the characteristics of bipolar response. 0.95 Mn 0.15 O thin film devices require a stronger optical power density to produce a reverse current signal.

[0041] Comparative Example 3

[0042] (1) After etching the P-type Si, three layers of Mn doping (CH 3 COO 2 Zn ethanol solution was used to prepare N-type reverse doped films and forward doped films. The parameters of the reverse doped film are as x increases away from the PN junction.

[0043] The parameters of the forward doped film are: 0.10, 0.05, 0.00. As the distance from the PN junction increases, x is: 0.00, 0.05, 0.08;

[0044] (2) making a mask, and magnetron sputtering an ITO electrode on the surface of the doped ZnO film, and magnetron sputtering an Al electrode on the back of the Si wafer;

[0045] (3) Connect the transparent ITO electrode on the top of the ZnO doped device to the Al electrode on the bottom to connect the device to the circuit. The power density is 0.2 mW cm -2 , 1.0mW cm -2 , 11.7 mW cm -2 The 633nm laser is used as the tested light source, and the spot area is 0.2mm -2 The current signal is recorded using a low-noise current preamplifier and a data acquisition card. It can be seen that both devices with two doping gradients have the characteristics of bipolar response, and the forward-doped thin-film device requires a stronger optical power density to produce a reverse current signal.

Claims

1. A doping concentration-dependent photocurrent bipolar response photodetector, characterized in that: The photodetector comprises a mutually coupled PN junction and a Schottky junction; the PN junction is composed of a ZnO semiconductor film uniformly doped with Mn and a hundred nanometers thick and a P-type Si; the Schottky junction is composed of a P-type Si and a bottom metal Al film; the response characteristic of the photodetector is that as the power density of the monochromatic light incident on the PN junction side gradually increases, the number of photons irradiated to the back Schottky junction increases, the generated photocurrent signal gradually reverses, and the power density inflection point corresponding to the photocurrent reversal is determined by the number of photons irradiated to the Schottky junction; the power density inflection point is determined by the absorption of light waves by the semiconductor film, and is related to the wavelength of the incident light, the Mn doping concentration in the ZnO semiconductor film constituting the photodetector, and the thickness of the semiconductor film. The inflection point position can be regulated by changing the Mn doping concentration.

2. A doping concentration gradient-dependent photocurrent bipolar response photodetector, characterized in that: The photodetector comprises a mutually coupled PN junction and a Schottky junction; the PN junction is composed of a hundred-nanometer-thick Mn gradient-doped ZnO semiconductor film and P-type Si; the Schottky junction is composed of P-type Si and a bottom metal Al film; the photodetector regulates the absorption of light waves of different wavelengths by the zinc oxide film by regulating the gradient size and direction of the Mn doping concentration, and regulates the number of photons irradiated to the back Schottky junction, thereby realizing a photocurrent bipolar response photoelectric sensor whose power density inflection point is regulated by the doping concentration gradient.

3. A method for realizing the doping concentration dependent photocurrent bipolar response photodetector as claimed in claim 1, characterized in that The implementation steps include: (1) A 5 μm thick P-type Si wafer with a resistivity of 1-20 Ωcm and a crystal plane orientation of (100) was ultrasonically cleaned with anhydrous ethanol and deionized water, and then etched in a mixed solution of 0.3 wt % NaOH and 8.0 v % isopropanol for 1 min to serve as a spin coating substrate; (2) According to the required doping concentration of Zn1-xMnxO film, (CH3COO)2Zn·2H2O and (CH3COO)2Mn·4H2O were weighed according to the required molar ratio, and the doping concentration x ranged from 0.00 to 0.

12. The weighed substances were dissolved in ethanol solution to obtain a 0.25 M solution, and ethylene glycol and ethanolamine were used as stabilizers in a volume ratio of 1:

1. The solution was stirred for 30-60 minutes and allowed to stand for more than 24 hours to be used as a spin coating precursor solution for later use; (3) Take 70 μL of the precursor solution and drop it on the Si substrate. The spin coating speed and duration are selected as low speed 600 rad / min (5s) and high speed 3000 rad / min (30s). After spin coating, place it on a heating table at 180°C to evaporate the solvent to form a film. Use the solution with the same doping concentration as the precursor and repeat the above steps three times to obtain a Zn1-x MnxO thin film; place the film-formed sample in a tubular furnace for annealing, fill it with argon at a flow rate of 190 sccm and oxygen at a flow rate of 10 sccm, anneal at 500°C for 1 hour, and maintain normal pressure in the tube; (4) using magnetron sputtering technology to deposit ITO and Al electrodes on the upper and lower surfaces of the annealed film, respectively, to obtain electrodes with a thickness of 100 to 300 nm; Complete the preparation of Al / p-Si / n-Zn1-x MnxO / ITO devices; (5) Connecting a copper wire to the device and accessing the circuit, and applying periodic illumination using light waves of different wavelengths without an external bias, can achieve the test of the optical power density inflection point of the photocurrent bipolar response device.

4. A method for realizing the doping concentration gradient dependent photocurrent bipolar response photodetector as claimed in claim 2, characterized in that The implementation steps include: (1) A 5 μm thick P-type Si wafer with a resistivity of 1-20 Ωcm and a crystal plane orientation of (100) was ultrasonically cleaned with anhydrous ethanol and deionized water, and then etched in a mixed solution of 0.3 wt % NaOH and 8.0 v % isopropanol for 1 min to serve as a spin coating substrate; (2) According to the required doping concentration of the Zn1-xMnxO film, (CH3COO)2Zn·2H2O and (CH3COO)2Mn·4H2O are weighed according to the required molar ratio, and the doping concentration x ranges from 0.00 to 0.12; the weighed substances are dissolved in an ethanol solution to obtain a 0.25M solution, and ethylene glycol and ethanolamine in a volume ratio of 1:1 are used as stabilizers, stirred for 30-60 minutes, and left to stand for more than 24 hours, and used as a spin coating precursor solution for standby use; (3) Take 70 μL of the precursor solution and drop it on the Si substrate. The spin coating speed and duration are selected as low speed 600 rad / min (5s) and high speed 3000 rad / min (30s). After spin coating, place it on a heating table at 180°C to evaporate the solvent to form a film. Select different doping concentrations of the precursor solution and repeat the above steps three times to obtain zinc oxide films with different Mn concentration gradient distributions; place the film-formed sample in a tubular furnace for annealing; (4) Using magnetron sputtering technology, ITO and Al electrodes are deposited on the top and bottom of the annealed film, respectively, to obtain electrodes with a thickness of 100 to 300 nm; thus completing the preparation of the doping concentration gradient distribution device; (5) Connecting a copper wire to the device and accessing it to an external circuit, and applying periodic illumination using light waves of different wavelengths without an external bias, the optical power density inflection point of the photocurrent bipolar response device can be tested.

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