A retinal-shaped photodetector for dynamic target detection

Abstract

A retina-shaped photodetector capable of dynamic target detection belongs to the field of photodetectors. The photodetector comprises, from top to bottom, an upper electrode (1), an insulating layer (2), a light absorption layer (3), and a lower electrode (4). The upper electrode is made of titanium and gold, the insulating layer is made of silicon dioxide, the light absorption layer is made of intrinsic silicon, and the lower electrode is made of copper. The upper electrode (1) is arranged in multiple independent closed loops, and the number of closed loops corresponds to the number of pixels of the image sensor. The more the number is, the clearer the image detection result can be achieved. Lead wires are drawn on one side of each closed loop. Each closed loop structure comprises a 10 nm thick titanium lower layer and a 70 nm thick gold upper layer. The photodetector does not output a signal for an unchanged light intensity signal, but outputs a pulse electrical signal when the light intensity changes. The pulse intensity is directly proportional to the ratio of the light intensity before and after the change.

Description

Technical fields:

[0001] This invention belongs to the field of photodetectors, specifically a retinal-shaped photodetector capable of detecting dynamic targets. Background technology:

[0002] With the development of the Internet of Things (IoT), the detection and identification of moving targets has become increasingly important. Traditional dynamic target detection systems are based on the traditional von Neumann architecture, where detection, storage, and data processing are separated. This architecture results in a large amount of useless signals being transmitted from the detector to the processor via a data bus. Both the transmission and processing processes increase energy consumption. In recent years, a new detector architecture has been developed—computation is performed internally within the detector (integrated sensing and computing). However, most current integrated sensing and computing systems utilize newly developed semiconductor materials such as two-dimensional materials or perovskites, which inevitably face incompatibility issues with current mature silicon processes. Therefore, it is essential to realize a dynamic target detector based on an integrated sensing and computing structure that is compatible with silicon processes. The human visual system is a highly efficient dynamic target detection system, where the Y-ganglion cells in the retina respond only to changing light intensity signals, greatly reducing the amount of information transmitted to the brain for data processing. Furthermore, the retinal response to light intensity has a logarithmic relationship with light intensity, allowing the degree of light intensity change to be directly obtained from the magnitude of the light response rather than the absolute value of the light intensity. Simulating the working mechanism of the human visual system will help achieve efficient dynamic target detection.

[0003] Capacitors can be used to block static signals while allowing changing signals to pass through. Furthermore, photosensitive chemical capacitors composed of a metal / insulator / semiconductor can achieve a logarithmic response to light intensity. Therefore, the light intensity response of the human visual system can be simulated using a metal / insulator / semiconductor structure. Summary of the Invention:

[0004] To address the problems existing in current technology centers, the purpose of this invention is to realize a silicon-compatible dynamic target detector by simulating the light intensity response characteristics of the human visual system. Its significant advantage is that the detector does not output a signal for a constant light intensity signal, but when the light intensity changes, the detector outputs a pulse electrical signal, with the pulse intensity being directly proportional to the ratio before and after the light intensity change.

[0005] A photodetector, characterized in that: the photodetector comprises, from top to bottom, an upper electrode (1), an insulating layer (2), a light-absorbing layer (3), and a lower electrode (4), wherein the upper electrode is made of titanium and gold, the insulating layer is made of silicon dioxide, the light-absorbing layer is made of intrinsic silicon, and the lower electrode is made of copper.

[0006] The upper electrode (1) is composed of multiple independent closed-loop arrangements. The number of closed loops corresponds to the number of pixels of the image sensor. The more the number, the clearer the image detection result can be achieved. And leads are led out from one side of each closed loop. Each closed-loop structure: the lower layer is titanium with a thickness of 10 nm, and the upper layer is gold with a thickness of 70 nm.

[0007] The closed-loop structure is preferably in the shape of a "square", with a side length of 500 μm and a line width of 10 μm.

[0008] The insulating layer (2) is silicon dioxide with a thickness of 300 nm, formed on the surface of the light absorption layer (3) by dry oxygen oxidation.

[0009] The light absorption layer (3) is intrinsic silicon with a thickness of 500 μm, a resistivity greater than 10,000 Ω·cm, and a size of 1 cm × 1 cm.

[0010] The lower electrode (4) is copper, directly contacting the light absorption layer (3), with a size of 2 cm × 5 cm.

[0011] The preparation method of the photodetector described above is characterized in that the preparation method includes the following steps:

[0012] a. Silicon dioxide is prepared on the upper surface of intrinsic silicon by dry oxidation; one side of the intrinsic silicon is connected to the copper electrode;

[0013] b. Fabricate the upper electrode

[0014] On the upper surface of the device obtained in a, the corresponding metal is deposited by electron beam evaporation as the upper electrode. The metal layer is uniform and the purity is greater than 99 wt%. The closed-loop shape of the upper electrode is preferably in the shape of a "square", and a lead is led out from one side to be connected to an external test circuit;

[0015] The other side of the intrinsic silicon is connected to the fabricated copper electrode.

[0016] The preparation of the upper electrode is specifically to spin-coat photoresist on the obtained silicon / silicon dioxide substrate, obtain the inverse pattern of the corresponding electrode pattern through lithography technology, then remove the exposed photoresist with a developer, and then uniformly deposit titanium with a thickness of 10 nm and gold with a thickness of 70 nm on the photoresist by electron beam evaporation technology. Then, soak in an acetone solution to remove the excess photoresist and excess metal, and obtain the electrode with the corresponding pattern.

[0017] The upper electrode and the lower electrode are respectively connected to a source meter, the voltage of the source meter is 0 V, and the change of the test current is measured.

[0018] The feature during the test is that the light source is incident from within the closed loop of the upper electrode, such as the "square" shape.

[0019] That is, the simulation of the light intensity response of the human visual system can be achieved. Brief Description of the Drawings:

[0020] Figure 1 It is a schematic diagram of the device structure

[0021] Figure 2 It is a light intensity response graph

[0022] Figure 3 It is a test schematic diagram

[0023] Figure 4 It is a test of a moving trolley Specific implementation method:

[0024] For the convenience of understanding, a specific case is introduced below in conjunction with the attached drawings: using this detector to detect a moving trolley

[0025] (1) As shown in Figure 1 , an upper electrode is fabricated on intrinsic silicon using photolithography technology and electron beam evaporation technology. The specific method is to spin-coat a photoresist (negative resist) on the silicon wafer, expose it for 1.2 s with ultraviolet light through a mask plate and perform flood exposure for 22 s, then develop it, and then evaporate a gold electrode using the electron beam evaporation method with an evaporation rate of 2 Å / s and a current value of 12 A. Finally, the photoresist is removed by the lift-off process to form a top electrode on the substrate. The obtained top electrode has a "square" shape, and a lead is led out on one side. The side length of the "square" is 500 μm, the line width is 10 μm, and the number of "square" electrodes corresponds to the number of pixels of the image sensor. The more the number, the clearer the image detection result can be achieved

[0026] (2) Place the above sample on the copper plate of the optoelectronic test platform, connect the upper electrode and the copper plate to the semiconductor analyzer respectively, and test the change of current with time

[0027] (3) Project the moving image of the dynamic trolley onto the detector and test the change of current on the detector

[0028] Experimental data:

[0029] Since the movement of the trolley will cause a change in the light intensity irradiated on the detector. In this example, the front end of the trolley will become darker and the rear end will become brighter. Negative pulse signals will be generated in the corresponding pixels at the front end of the trolley, while positive pulse signals will be generated at the rear end. By integrating all pixels, the contour of the trolley movement can be obtained. This detector has no response to the static background, and the information is unified to be the same. That is, the detection of moving targets is achieved

Claims

1. A photodetector, characterized by: The photoelectric detector comprises, from top to bottom, an upper electrode (1), an insulating layer (2), a light absorption layer (3), and a lower electrode (4), wherein the upper electrode is titanium and gold, the insulating layer is silicon dioxide, the light absorption layer is intrinsic silicon, and the lower electrode is copper. The upper electrode (1) is arranged in multiple independent closed loops, and the number of the closed loops corresponds to the number of pixels of the image sensor, and the more the number of the closed loops, the clearer the image detection result can be achieved. A lead wire is led out from one side of each closed loop.

2. A photodetector as claimed in claim 1, characterized in that: Each closed loop structure comprises a 10-nm-thick titanium lower layer and a 70-nm-thick gold upper layer.

3. A photodetector as claimed in claim 1, wherein: The closed loop structure is a "mouth" shape, with a side length of 500 μm and a line width of 10 μm.

4. A photodetector as claimed in claim 1, characterized in that: The insulating layer (2) is 300-nm-thick silicon dioxide formed on the surface of the light absorption layer (3) by a dry oxygen oxidation method.

5. A photodetector as claimed in claim 1, characterized in that: The light absorption layer (3) is 500-μm-thick intrinsic silicon with a resistivity greater than 10,000 Ω·cm and a size of 1 cm×1 cm.

6. A photodetector as claimed in claim 1, characterized in that: The lower electrode (4) is copper, which directly contacts the light absorption layer (3) and has a size of 2 cm×5 cm.

7. The method for fabricating a photodetector according to claim 1, characterized in that, The method comprises the following steps: a. The upper surface of the intrinsic silicon is prepared with a surface silicon dioxide by a dry oxidation method; one side of the intrinsic silicon is connected with a copper electrode; b. The upper electrode is prepared The corresponding metal is used as the upper electrode on the upper surface of the device obtained in a by electron beam evaporation, the metal layer is uniform and has a purity greater than 99 wt%, the upper electrode closed loop shape is a "mouth" shape, and a lead wire is led out from one side to be connected with an external test circuit; The other side of the intrinsic silicon is connected with a prepared copper electrode; The preparation of the upper electrode specifically comprises the following steps: spin coating a photoresist on the obtained silicon / silicon dioxide substrate, obtaining a reverse pattern corresponding to the electrode pattern by a photolithography technology, removing the exposed photoresist with a developing solution, uniformly evaporating titanium with a thickness of 10 nm and gold with a thickness of 70 nm on the photoresist by an electron beam evaporation technology, and then soaking in an acetone solution to remove the excess photoresist and excess metal, to obtain the corresponding pattern electrode.

8. The application of the photoelectric detector of claim 1, wherein the upper electrode and the lower electrode are respectively connected with a source table, the voltage of the source table is 0 V, and the change of a test current is tested; The feature in the test process is a light source, which is incident from the inside of the closed loop of the upper electrode; that is, the simulation of the light intensity response of the human visual system can be achieved.

Images