Vertical ITO / black silicon photodetector and preparation method thereof

Abstract

Vertical ITO / black silicon photodetector and preparation method thereof, relate to the technical field of photoelectric device imaging, and particularly to a preparation technology of a high-performance vertical ITO / black silicon visible-near infrared photodetector. The photodetector is based on an n-type silicon substrate, and the front surface is a p-type layer with high doping concentration. The n-type layer on the back surface of the device is a supersaturatedly doped black silicon layer, and a transparent electrode ITO is covered on the surface of the black silicon to improve the surface characteristics of the black silicon microstructure, suppress surface recombination, and enhance the separation of carriers, so as to improve the photoelectric response performance of the photodetector. The device structure is vertical, and has high integration. By using ITO as the electrode on the surface of the black silicon microstructure, surface recombination can be well suppressed, the separation of photo-generated carriers can be enhanced, the device has high photoelectric response performance, and has important application prospects in the development of low-cost silicon-based infrared detectors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optoelectronic device imaging, and particularly to a preparation technology of a high-performance vertical ITO / black silicon visible-near infrared photodetector. BACKGROUND

[0002] Silicon, as a kind of abundant semiconductor material, has been widely used. In the field of photoelectric detection, silicon-based devices are mainly used for imaging in the visible light range. This is mainly because silicon is an indirect bandgap material, and its bandgap is 1.12 eV, which limits its application in the field of high-performance infrared detection. In view of this problem, researchers have also studied some special material systems, such as InGaAs, HgCdTe and Ge materials, which exhibit excellent imaging performance, especially in the near-infrared and short-wave infrared range. However, there are also some problems. These materials have poor compatibility with standard silicon process devices, and the preparation cost is high, which is not suitable for low-cost imaging fields. The emergence of black silicon has opened up a new direction to solve this problem.

[0003] The over-doping of black silicon introduces impurity energy levels, which can expand the spectral response range of silicon-based devices. The light-trapping effect of its microstructure can enhance the performance of the device. For silicon-based photodetector devices, PN junction is a very common device structure, and PIN photodetector is developed from PN photodetector. PIN photodetector has the characteristics of working at room temperature, high energy resolution, short pulse rise time, high detection efficiency, and stable performance, and is currently playing an irreplaceable role in the fields of medical CT, security inspection, industrial non-destructive testing, oil well logging, radioactivity detection, environmental monitoring and infrared touch screen.

[0004] There are also many silicon-based PIN structure devices reported, such as a 1064nm enhanced Si-PIN photodetector and its manufacturing method disclosed in patent CN106129145A. However, for traditional device structures, the preparation of black silicon microstructure increases its surface area, which causes serious surface recombination, which is not conducive to the preparation of high-performance devices. Growing a passivation layer on the surface of the microstructure can effectively reduce the surface recombination, but it is not conducive to the formation of good ohmic contact. ITO is a commonly used transparent electrode, and has high transmittance in the visible-near infrared range. Using ITO as the electrode layer of the black silicon layer can suppress surface recombination and enhance the transport of photo-generated carriers, thereby improving the performance of the black silicon device. SUMMARY

[0005] The present application aims to solve the problems of serious surface recombination of traditional black silicon device microstructure and poor transport of photo-generated carriers. By depositing ITO on the surface of the microstructure, surface recombination is suppressed, and the photoelectric response performance of the device in the visible-near infrared range is improved.

[0006] The vertical ITO / black silicon photodetector is characterized in that the detector is from bottom to top an ITO electrode layer, a microstructure black silicon layer, an n-type silicon substrate layer, a p-type layer, and an Al metal layer.

[0007] The p-type layer is a heavily doped p-type layer formed by injecting B elements or As elements on one side of the silicon substrate.

[0008] The microstructure black silicon layer is formed by over-saturation doping black silicon on the other side of the n-type silicon substrate layer through femtosecond laser or reactive ion etching.

[0009] The thickness of the ITO is 10-20 nm, and the thickness of the n-type silicon substrate layer is 50-200 microns.

[0010] The microstructure black silicon layer is formed after high-temperature annealing at 850-900°C for 30 minutes, repairing the damaged crystal lattice, and activating the doped atoms.

[0011] The n-type silicon substrate has a resistivity of 10-10000 Ω·cm and a thickness of 50-200 microns, and is cleaned before ion implantation.

[0012] The ion implantation needs to grow a 100-200 nm SiO2 layer before implantation to reduce implantation damage. The implantation energy is 130-160 keV, the implantation dose is -10 14 cm -2 , and the doping concentration after implantation reaches 10 19 -10 20 cm -3 .

[0013] The black silicon is prepared by femtosecond laser, and the over-saturation doping type is n-type with a doping concentration of -10 20 cm -3 .

[0014] The substrate is thinned by mechanical grinding and polishing, and the thickness after thinning is 50-200 microns. A too thick substrate layer is not conducive to the collection of photo-generated carriers.

[0015] The preparation method of the vertical ITO / black silicon photodetector is characterized by comprising the following steps:

[0016] Step 1, cleaning the n-type silicon substrate;

[0017] Step 2, after cleaning, preparing a SiO2 thin film on the n-type silicon substrate with a thickness of 100-200 nm;

[0018] Step 3, B element or As element implantation on SiO2 film, implantation energy is 160 keV, dose is -10 14 cm -2 ;

[0019] Step 4, black silicon is prepared on the other side of Si substrate by femtosecond laser or reactive ion etching method;

[0020] Step 5, annealing at 850-900℃ for 20-40min in rapid annealing furnace, taking out, removing SiO2 film by wet method;

[0021] Step 6, ITO electrode is prepared on the surface of microstructure black silicon;

[0022] Step 7, p-type ohmic metal Al is prepared.

[0023] Compared with the existing vertical PIN device, the ion implantation technology and the preparation of black silicon layer are adopted to construct the basic structure of p / n / n + / ITO, the black silicon device with excellent rectification characteristics and response characteristics is prepared. The ITO realizes the functions of passivation and contact electrode, the surface recombination of black silicon microstructure is inhibited, the transport of photo-generated carriers is enhanced, and the device has high response performance in the visible-near infrared range. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structure schematic diagram of the detector of embodiment 1.

[0025] Figure 2 It is a preparation flow chart of the detector.

[0026] Figure 3 It is the dark current test of the detector of embodiment 1 and the response I-V curve under the 940nm LED light source.

[0027] Figure 4 It is the response rate of the detector of embodiment 1 under the 940nm LED light source.

[0028] Figure 5 It is the corresponding quantum efficiency of the detector of embodiment 1.

[0029] Figure 6 It is the corresponding specific detectivity of the detector of embodiment 1.

[0030] Among them, the ITO electrode layer 1, the microstructure black silicon layer 2, the n-type silicon substrate layer 3, the p-type layer 4 and the Al metal layer 5. DETAILED DESCRIPTION

[0031] The application will be further described below in combination with the embodiments.

[0032] Embodiment 1: Vertical ITO / Black Silicon photodetector, from bottom to top, ITO electrode layer 1, microstructure black silicon layer 2, n-type silicon substrate layer 3, p-type layer 4, Al metal layer 5.

[0033] The preparation method of the vertical ITO / Black Silicon photodetector comprises the following steps:

[0034] Step 1: The n-type silicon wafer substrate is soaked in a mixed solution of hydrogen peroxide, ammonia and deionized water in a volume ratio of 1:1:3 at 80°C for 30 minutes, then washed with deionized water and dried; the resistivity of the n-type silicon wafer substrate is 10-10000 Ω·cm, and the thickness is 50-200 μm;

[0035] Step 2: A 100 nm SiO2 film is prepared on the cleaned Si substrate.

[0036] Step 3: B ion implantation is performed on the SiO2 film, the implantation energy is 160 keV, and the dose is -10 14 cm -2 .

[0037] Step 4: Black silicon is prepared on the other side of the Si substrate using femtosecond laser.

[0038] Step 5: Annealing at 900°C for 30 minutes in a rapid annealing furnace, then removing the SiO2 film by wet method.

[0039] Step 6: ITO electrode is prepared on the microstructure black silicon surface.

[0040] Step 7: P-type ohmic metal Al is prepared.

[0041] Step 8: Lead electrode wire.

[0042] The above-mentioned vertical ITO / Black Silicon visible-near infrared photodetector involves raw materials that can be obtained by general methods, and one or more steps mentioned in the present application do not exclude that the combination step also has other methods and operation processes; it should also be noted that this example is only used to illustrate the feasibility of the present application, but not to limit the scope of the present application. In addition, without substantial changes in the preparation technology, it is also considered as the implementable scope of the present application.

Claims

1. A vertical ITO / black silicon photodetector, characterized in that... The detector consists of, from bottom to top, an ITO electrode layer, a microstructured black silicon layer, an n-type silicon substrate layer, a p-type layer, and an Al metal layer; The p-type layer is a heavily doped p-type layer formed by implanting B or As elements into one side of a silicon substrate; The aforementioned microstructured black silicon layer is formed on the other side of an n-type silicon substrate by femtosecond laser or reactive ion etching, which is then supersaturated and doped with black silicon.

2. The vertical ITO / black silicon photodetector as described in claim 1, characterized in that... The thickness of ITO is 10-20 nm; the resistivity of the n-type silicon substrate is 10-10000 Ω·cm, and the thickness is 50-200 micrometers.

3. A method for fabricating a vertical ITO / black silicon photodetector, characterized in that... Includes the following steps: Step 1: Clean the n-type silicon substrate; Step 2: After cleaning, a SiO2 thin film with a thickness of 100-200 nm is prepared on the n-type silicon substrate. Step 3: Implant B or As elements onto the SiO2 thin film at an energy of 160 keV and a dose of -10. 14 cm -2 ; Step 4: Prepare black silicon on the other side of the Si substrate using femtosecond laser or reactive ion etching. Step 5: Anneal at 850-900℃ for 20-40 minutes in a rapid annealing furnace, remove and wet remove the SiO2 film; Step 6: Fabricate ITO electrodes on the microstructured black silicon surface; Step 7: Prepare p-type ohmic metal Al.

Images