A self-powered photodetector with enhanced gradient interfacial state

Abstract

The application discloses a kind of gradient interface state's implementation method and a kind of gradient interface state enhanced self-powered photoelectric detector, including p-Si base, gradient interface state distribution n-type oxide semiconductor film and conductive electrode;The gradient interface state distribution is obtained by the method of simultaneously applying bias voltage and ultraviolet light irradiation, the concentration of negative interface state obtained along p-n junction interface increases towards the top electrode direction, reduces interface transfer resistance, obtains enhanced p-n junction equivalent built-in electric field, and then reduces the recombination probability of carrier at interface, improves pyroelectric photoelectron effect, improves the transient transport efficiency of photo-generated carrier.The gradient interface state generation method has the characteristics of flexibility, easy to implement;The responsivity and detection capability of the gradient interface state enhanced self-powered photoelectric detector are significantly improved compared with uniform interface state distribution, and the enhancement effect has the characteristics of being generally applicable in ultraviolet-visible-near infrared light region, and can be widely applied to thermal imaging, environmental monitoring, intelligent agriculture, biomedical, missile guidance and space communication and other civil and military fields.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection, and particularly relates to a method for realizing gradient interface states and a self-powered photoelectric detector with enhanced gradient interface states. Background Technology

[0002] With the rapid development of optical information technology, semiconductor photodetectors are widely used in civilian and military fields such as thermal imaging, environmental monitoring, smart agriculture, biomedicine, missile guidance, and space communication. However, it is worth noting that the additional surface energy levels generated by the inherent surface electronic states of oxide semiconductors inevitably lead to recombination of photogenerated carriers at the interface in self-powered photodetectors, significantly reducing the photodetector's response capability and detection performance. Therefore, seeking reasonable and efficient strategies for controlling the surface and interface states of oxide semiconductors is an effective solution to improve the performance of self-powered photodetectors.

[0003] Currently, methods for controlling semiconductor interface states mainly include semiconductor material modification and the introduction of heterojunction interface physical effects. Semiconductor material modification mainly includes hydrogenation, surface passivation, heat treatment, ion implantation, and ultraviolet irradiation. Among these, ultraviolet irradiation, as a non-contact and flexible control scheme, can achieve rapid removal and processing of interface states. Researchers have already used ultraviolet irradiation to control interface states in zinc oxide-based heterojunction devices, improving the transient response performance of self-powered photodetectors. Regarding heterojunction interface physical effects, pyroelectric optoelectronic effects utilize the photo-induced pyroelectric effect in non-centrosymmetric materials to change the polarization charge at the interface, thereby achieving rapid transfer of photogenerated carriers and efficient signal collection at the interface. To further improve the response performance of self-powered photodetectors, it is necessary to further control the distribution of interface states and increase the built-in electric field; introducing a suitable distribution of interface states in the heterojunction region will help increase the built-in electric field. Therefore, synergistically utilizing non-uniformly distributed surface and interface states and pyroelectric optoelectronic effects to modulate interface states in heterojunction junction regions is an important way to improve the response performance of self-powered photodetectors and has significant application value for realizing self-powered photodetectors. Summary of the Invention

[0004] The purpose of this invention is to propose a method for realizing gradient interface states and a self-powered photodetector with enhanced gradient interface states. For the realized zinc oxide-based photodetector, the interface states are effectively reduced and non-uniformly distributed by irradiating zinc oxide with ultraviolet light under bias conditions. The spatial gradient of the interface state concentration induces an additional electric field in the junction region in the same direction as the built-in electric field, increasing the equivalent built-in electric field at the junction region. This enhances the effective separation of photogenerated carriers and the photo-induced pyroelectric effect, significantly improving the responsivity and detectivity of the transient photocurrent response of the p-Si / n-ZnO photodetector.

[0005] This invention discloses a method for realizing gradient interface states, characterized by applying a bias voltage to the upper and lower surfaces of a zinc oxide film, and simultaneously irradiating the zinc oxide film with ultraviolet light to change the distribution of negative oxygen ions inside, thereby reducing the number of negatively charged interface states inside the zinc oxide film, thus forming a stable interface state distribution within the zinc oxide film. This invention discloses a self-powered photodetector with gradient interface state enhancement. The photodetector comprises a p-Si substrate, an n-type oxide semiconductor thin film with gradient interface state distribution, and conductive electrodes. The p-Si substrate and the n-type oxide semiconductor thin film with gradient interface state distribution form a pn heterojunction, and conductive thin film electrodes are deposited at both ends of the pn heterojunction. The interface state concentration increases along the pn junction interface towards the top electrode, resulting in a smaller interface transfer resistance, which is beneficial for photogenerated carrier transport, obtaining a larger equivalent built-in electric field, and enhancing the transient response performance of the photodetector. The n-type oxide semiconductor thin film with gradient interface state distribution is characterized in that it can be a ZnO thin film, constructing a p-Si / n-ZnO heterostructure. The interface state concentration gradually increases along the pn junction interface towards the ZnO and electrode contact end, inducing an additional electric field in the interface-oxide semiconductor that is in the same direction as the built-in electric field, thereby improving the detection capability of the self-powered photodetector.

[0006] Compared with existing self-powered photodetectors with interface state distribution, the present invention has the following advantages:

[0007] 1. In the constructed p-Si / n-ZnO heterojunction photodetector, the surface state distribution inside zinc oxide can be directly controlled based on the method described in this invention; in the presence of a heterojunction interface, the gradient interface state distribution can be obtained by ultraviolet irradiation and the application of a bias voltage. This method has the advantages of being flexible and easy to implement; and it has a certain control effect on different zinc oxide samples.

[0008] 2. In the constructed p-Si / n-ZnO heterojunction photodetector, the gradient interface states can lead to a smaller interface transfer resistance, a larger built-in potential, a reduced recombination probability of carriers at the interface, and an improved transport efficiency of photogenerated carriers. This significantly enhances the steady-state photocurrent and transient photocurrent of the photodetector, thereby improving the responsivity and detection capability of the steady-state and transient responses.

[0009] 3. The gradient interface state-enhanced p-Si / n-ZnO self-powered photodetector, under excitation with 633nm light, exhibits a photoresponsivity of 13.8 mAW corresponding to the maximum transient peak-to-peak photocurrent. -1 The detection rate can reach 4.6×10 11Jones, compared to the device with the initial interface state, showed a 123% improvement in responsivity and detectivity. Therefore, the gradient interface state generation method in this invention can reasonably and effectively control the interface state, thereby improving the detector's responsivity and detection capability.

[0010] 4. The gradient interface state realized by this invention can enhance the detection capability of the corresponding photodetector in the quasi-monochromatic light range of 300-1085nm, and has the characteristics of being universally applicable in the ultraviolet-visible-near-infrared light region. Moreover, the realized detector can operate stably in a vacuum environment for a long time. The gradient interface state enhanced self-powered photodetector in this invention has good application potential in wide spectrum, vacuum environment and weak signal detection. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the device for realizing gradient interface states in this invention. In the figure: 1.1 is a p-Si single crystal substrate, 1.2 is a ZnO thin film, 1.3 is an ITO top electrode, 1.4 is an ITO bottom electrode, and a DC voltage is applied between 1.3 and 1.4 while the ZnO thin film is irradiated with ultraviolet light.

[0012] Figure 2 This is a schematic diagram of a self-powered photodetector based on gradient interface state enhancement. In the diagram: 1.1 is the p-Si single-crystal substrate, and 1.2 is the gradient interface...

[0013] A ZnO thin film with planar distribution, where 1.3 is the ITO top electrode and 1.4 is the ITO bottom electrode.

[0014] Figure 3 The photoelectric properties of self-powered photodetectors with different interface state distributions for 633nm laser light described in Example 1, Comparative Example 1, and Comparative Example 2 are as follows:

[0015] Flow response curve.

[0016] Figure 4 The responses of self-powered photodetectors to 633nm laser light under different interface state distributions as described in Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0017] Degree comparison chart.

[0018] Figure 5 This refers to the detection of 633nm laser light by self-powered photodetectors under different interface state distributions as described in Example 1, Comparative Example 1, and Comparative Example 2.

[0019] Rate comparison chart.

[0020] Figure 6This is a comparison of the transient response photocurrents of self-powered photodetectors with different interface state distributions described in Example 1, Comparative Example 1, and Comparative Example 2 to quasi-monochromatic light with wavelengths in the range of 300-1085nm.

[0021] Figure 7 The ZnO thin film assembled device prepared by magnetron sputtering as described in Example 2 exhibits performance in the initial state, uniform interface state, and gradient interface state.

[0022] Comparison of photocurrent response curves for 633nm laser.

[0023] Figure 8 This is a comparison of the photocurrent response curves of the ZnO thin film assembled device prepared by the hydrothermal method described in Example 3 to 633nm laser in the initial state, uniform interface state, and gradient interface state. Detailed implementation method:

[0024] The technical details of the present invention will be further described below with reference to the accompanying drawings, but this is not limited thereto. Any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the main spirit and scope of the technical solutions of the present invention should be covered within the protection scope of the present invention.

[0025] I. Preparation process of the device of the present invention

[0026] (1) Cut the purchased p-type Si wafer (100) with a thickness of 500μm and a resistivity of 1-20Ωcm into pieces of about 1.0cm×1.0cm, and clean the surface dust with deionized water and anhydrous ethanol respectively. Place the clean Si wafer in a mixed solution of 0.3wt% NaOH and 8.0v% isopropanol for 1min for etching, and use it as a spin-coating substrate.

[0027] (2) Prepare a 0.05M (CH3COO)2Zn ethanol solution, and use ethylene glycol and ethanolamine in a volume ratio of 1:1 as stabilizers. Stir at room temperature for 40-60 min, and then let stand for more than 48 h to obtain a precursor solution for spin coating.

[0028] (3) Take 50-70 μL of the precursor solution in (2) above and drop it onto the p-Si wafer etched in (1) above. Spin coat at a low speed of 600 rad / min for 5 s and at a high speed of 2000-3000 rad / min for 30 s. Place it on a heating stage at 180℃ to evaporate the solvent and form a film. Repeat the above steps to obtain a ZnO precursor film with 2 spin coatings. Place the ZnO precursor film in a tube furnace for annealing at 400-600℃ for 1 h. The flow ratio of argon to oxygen in the tube furnace is 19:1. The tube is kept at atmospheric pressure to obtain a ZnO film with a thickness of about 100 nm.

[0029] (4) ITO electrodes were deposited on the surface of p-Si and n-ZnO thin films using magnetron sputtering technology. The cavity pressure was 1-5 Pa, the sputtering power was 80-100 W, the argon flow rate was 40 sccm, and the sputtering was continued for 15 min to obtain the ITO top electrode and bottom electrode. Silver paste was applied to the electrode positions and copper wires were connected to them to obtain the initial state of p-Si / n-ZnO self-powered photodetector.

[0030] (5) Irradiate the above (4) device with ultraviolet light with a wavelength of 325nm in a vacuum environment for 30-120s. At the same time as the ultraviolet light irradiation, apply a DC voltage of 0.3-1.6V to both ends of the device, where the ZnO end is "+" and the Si end is "-". Under the ultraviolet light irradiation, photogenerated carriers are generated in ZnO. Among them, the photogenerated holes will combine with the negative oxygen ions in zinc oxide to generate O2, reducing the concentration of negative oxygen ions. Under the above bias conditions, the local potentials in different places are different, so the concentration of negative oxygen ions in zinc oxide will gradually increase from the junction region to the top electrode. This is equivalent to the concentration of negatively charged interface states increasing in this direction, thus obtaining a self-powered photodetector with gradient interface state distribution. When only ultraviolet light is used to irradiate the device, a self-powered photodetector with effective reduction and uniform distribution of interface states is obtained.

[0031] (6) Under the condition of no external power supply, the photodetector is excited by light pulses of different power densities and wavelengths, and the photocurrent response of the device is recorded, thereby realizing the self-powered detection of light waves of different wavelengths and light intensities.

[0032] II. The present invention will be described in detail below with specific embodiments.

[0033] Example 1

[0034] (1) A ZnO film with a thickness of about 100 nm was obtained by spin-coating (CH3COO)2Zn precursor solution twice on an etched Si wafer.

[0035] (2) A conductive electrode with a thickness of about 150 nm is magnetron sputtered on the top of the ZnO thin film and on the Si wafer, and an external copper wire electrode is connected.

[0036] (3) In an air or vacuum environment, using methods such as Figure 1 The device shown applies a DC voltage of 1.0V to both ends of the device and simultaneously irradiates a zinc oxide thin film with ultraviolet light of wavelength 325nm for 30-120s to obtain a self-powered photodetector with gradient interface state distribution.

[0037] (4) For p-Si / n-ZnO devices with gradient interface state distribution, excitation is performed using a 633nm laser or quasi-monochromatic light with a center wavelength in the range of 300-1085nm, with a spot area of ​​approximately 0.35cm². 2The generated current signals are collected and recorded using a low-noise, small-signal ammeter and a data acquisition card.

[0038] Comparative Example 1

[0039] Compared with Example 1, this example only uses 325nm ultraviolet light to irradiate the device for 30-120s to obtain a self-powered photodetector with uniformly distributed interface states. The photoelectric signal acquisition is the same as in Example 1.

[0040] Comparative Example 2

[0041] Compared with Example 1, this example does not use ultraviolet light irradiation and does not apply voltage, thus obtaining a self-powered photodetector with the interface state as the initial state, and the photoelectric signal acquisition is the same as in Example 1.

[0042] Example 2

[0043] Compared with Example 1, the ZnO thin film in the p-Si / n-ZnO heterojunction of this example is prepared by magnetron sputtering, which is different from the sol-gel method used in Example 1. The radio frequency power is controlled in radio frequency mode, a certain argon and oxygen flow ratio is maintained, and sputtering is performed for 20 minutes to obtain a ZnO thin film with a thickness of about 100 nm.

[0044] Example 3

[0045] Compared with Example 1, the ZnO film in the p-Si / n-ZnO heterojunction of this example is obtained by hydrothermal method. The silicon wafer containing the ZnO seed layer is placed in a mixed solution of zinc nitrate and hexamethylenetetramine with a concentration ratio of 1:1 and grown for 30 min to prepare a ZnO film with a thickness of about 100 nm. The method of realizing the zinc oxide film in this example is different from the sol-gel method in Example 1.

[0046] The photocurrent response of self-powered photodetectors with different interface state distributions to 633nm laser light was recorded using a low-noise, small-signal detection ammeter and a data acquisition card in Examples 1 and 2. Figure 3 As shown, compared to the device in its initial state, the transient photocurrent response of the uniform interface state device irradiated with ultraviolet light is larger. Simultaneously, the transient photocurrent response of the gradient interface state device obtained after applying a bias voltage and ultraviolet light irradiation is the largest, indicating that the gradient interface state can enhance the response performance of pyroelectric optoelectronic detectors; Figure 4 and Figure 5 As shown, under excitation by 633nm lasers of different power densities, the maximum transient responsivity of the gradient interface state device was improved by 123% and 28% compared to the initial state and uniform interface state devices, respectively, and the maximum transient detectivity was improved by 123% and 28%, respectively; Figure 6As shown, under quasi-monochromatic light excitation with center wavelengths in the range of 300-1085 nm, the transient photocurrent response of the gradient interface state device to ultraviolet-visible-near-infrared light is greater than that of the uniform interface state device and the initial device; for example Figure 7 As shown, the steady-state photovoltaic current of the zinc oxide-based device fabricated by magnetron sputtering in the gradient interface state is increased by 68% and 15% compared to the initial state and the uniform interface state, respectively, and the corresponding peak-to-peak transient current is increased by 314% and 130% compared to the initial state and the uniform interface state, respectively; Figure 8 As shown, the steady-state photovoltaic current of the zinc oxide-based device prepared by the hydrothermal method in the gradient interface state is increased by 257% and 52% compared with the initial state and the uniform interface state, respectively. The corresponding peak-to-peak transient current is increased by 39% and 23% compared with the initial state and the uniform interface state, respectively. The results show that the gradient interface state has a certain enhancement effect on the p-Si / n-ZnO heterojunction self-powered photodetector constructed by zinc oxide thin films obtained by different preparation methods.

Claims

1. A gradient-interfacial-state-enhanced self-powered photodetector, characterized in that: The photodetector comprises a p-Si substrate (1.1), an n-type oxide semiconductor ZnO thin film with gradient interface state distribution (1.2), a top electrode (1.3) of the n-type oxide semiconductor ZnO thin film, and a p-Si bottom electrode (1.4). The p-Si substrate and the n-type oxide semiconductor ZnO thin film with gradient interface state distribution form a pn heterojunction. The n-type oxide semiconductor ZnO thin film with gradient interface state distribution is formed by applying a bias voltage of 0.3-1.6 V between the top and bottom electrodes and simultaneously introducing ultraviolet light irradiation at the top. The gradient interface state distribution is characterized by an increase in interface state concentration along the pn junction interface towards the top electrode. The gradient interface state distribution can reduce the interface transfer resistance, obtain an enhanced equivalent built-in electric field in the junction region, thereby reducing the recombination probability of carriers at the interface and improving the pyroelectric photoelectronic effect.

2. A method for implementing the gradient-interfacial-state-enhanced self-powered photodetector of claim 1, characterized in that The implementation steps are as follows: (1) Cut a p-type Si wafer (100) with a thickness of 500 μm and a resistivity of 1-20 Ω cm into pieces of about 1.0 cm × 1.0 cm, and clean the surface dust with deionized water and anhydrous ethanol respectively. Place the clean Si wafer in a mixed solution of 0.3 wt% NaOH and 8.0 v% isopropanol for 1 min for etching, and use it as a spin-coating substrate; (2) Prepare a 0.05 M (CH3COO)2Zn ethanol solution, and use ethylene glycol and ethanolamine in a volume ratio of 1:1 as stabilizers. Stir at room temperature for 40-60 min, and then let stand for more than 48 h to obtain a precursor solution for spin coating. (3) Take 50-70 μL of the precursor solution in (2) above and drop it onto the p-Si wafer etched in (1) above. Spin coat at a low speed of 600 rad / min for 5 s and at a high speed of 2000-3000 rad / min for 30 s. Place it on a heating stage at 180 ℃ to evaporate the solvent and form a film. Repeat the above steps to obtain a ZnO precursor film with 2 spin coatings. Place the ZnO precursor film in a tube furnace for annealing at 400-600 ℃ for 1 h. The flow ratio of argon to oxygen in the tube furnace is 19:

1. The tube is kept at atmospheric pressure to obtain a ZnO film with a thickness of 80-120 nm. (4) Electrodes are deposited on the surface of p-Si and n-ZnO thin films using magnetron sputtering technology. The cavity pressure is 1-5 Pa, the sputtering power is 80-100 W, the argon flow rate is 40 sccm, and the sputtering is continued for 15 min to obtain the top electrode and bottom electrode. Silver paste is applied to the electrode positions and copper wires are connected to them to obtain the initial state of p-Si / n-ZnO self-powered photodetector. (5) In an air or vacuum environment, the device obtained in (4) above is irradiated with ultraviolet light at a wavelength of 325 nm for 30-120 s under a bias voltage of 1.0 V to prepare a self-powered photodetector with gradient interface state distribution. (6) Without an external power supply, a shutter and an attenuator are added in front of the photodetector. The photodetector is excited by light pulses of different wavelengths and power densities, and the corresponding photocurrent response is recorded. This enables the detection of different light waves by self-powered means.

3. A method for achieving a gradient distribution of interface states, characterized by: The implementation method includes a p-Si substrate (1.1), an n-type oxide semiconductor ZnO thin film (1.2), a top electrode (1.3), a bottom electrode (1.4), a bias voltage, and ultraviolet irradiation. The ultraviolet irradiation is a light wave with photon energy greater than the oxide bandgap, which generates photogenerated carriers in the oxide semiconductor thin film. The bias voltage is a voltage applied to the oxide semiconductor thin film, which regulates the spatial distribution of photogenerated carriers in the direction of the electric field generated by the bias voltage, thereby regulating the distribution of negative oxygen ions in the oxide semiconductor thin film, thus forming a gradient interface state distribution in the direction of the electric field, and obtaining an oxide semiconductor thin film with a gradient interface state distribution. The gradient interface state distribution is achieved by controlling the gradient direction of the interface state concentration by the direction of the bias voltage, and by controlling the irradiation energy density by changing the ultraviolet irradiation time to regulate the gradient magnitude of the interface state concentration.

4. A method for implementing the gradient interface state of claim 3, characterized by The implementation steps are as follows: (1) Cut a p-type Si wafer (100) with a thickness of 500 μm and a resistivity of 1-20 Ω cm into pieces of about 1.0 cm × 1.0 cm, and clean the surface dust with deionized water and anhydrous ethanol respectively. Place the clean Si wafer in a mixed solution of 0.3 wt% NaOH and 8.0 v% isopropanol for 1 min for etching, and use it as a spin-coating substrate; (2) Prepare a 0.05 M (CH3COO)2Zn ethanol solution, and use ethylene glycol and ethanolamine in a volume ratio of 1:1 as stabilizers. Stir at room temperature for 40-60 min, and then let stand for more than 48 h to obtain a precursor solution for spin coating. (3) Take 50-70 μL of the precursor solution in (2) above and drop it onto the p-Si wafer etched in (1) above. Spin coat at a low speed of 600 rad / min for 5 s and at a high speed of 2000-3000 rad / min for 30 s. Place it on a heating stage at 180 ℃ to evaporate the solvent and form a film. Repeat the above steps to obtain a ZnO precursor film with 2 spin coatings. Place the ZnO precursor film in a tube furnace for annealing at 400-600 ℃ for 1 h. The flow ratio of argon to oxygen in the tube furnace is 19:

1. The tube is kept at atmospheric pressure to obtain a ZnO film with a thickness of 80-120 nm. (4) Electrodes are deposited on the surface of p-Si and n-ZnO thin films using magnetron sputtering technology. The cavity pressure is 1-5 Pa, the sputtering power is 80-100 W, the argon flow rate is 40 sccm, and the sputtering is continued for 15 min to obtain the top electrode and bottom electrode. Silver paste is applied to the electrode positions and copper wires are connected to them to obtain the initial state of p-Si / n-ZnO self-powered photodetector. (5) Connect the top and bottom electrodes of the p-Si / n-ZnO self-powered photodetector in its initial state to the signal generator; (6) When the signal generator applies a DC voltage of 0.3~1.6 V between the top and bottom electrodes of the device, the device (5) is irradiated with ultraviolet light for 30-120 s, thereby increasing the concentration of interface states in the ZnO thin film along the pn junction interface towards the top electrode; when the signal generator applies a DC voltage of -0.3~-1.6 V between the top and bottom electrodes of the device, the device (5) is irradiated with ultraviolet light for 30-120 s, thereby decreasing the concentration of interface states in the ZnO thin film along the pn junction interface towards the top electrode; the concentration gradient of interface states in ZnO thin films with high voltage and long ultraviolet irradiation time is greater.

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