CN114566566A - Aluminum nitride solar blind photoelectric detector and preparation method thereof - Google Patents

Abstract

An aluminum nitride solar blind photoelectric detector and a preparation method thereof belong to the technical field of semiconductor photoelectric detection. The method comprises the steps of taking c-plane sapphire as a substrate, growing an aluminum nitride film on the substrate by adopting a reactive radio frequency magnetron sputtering technology, then improving the crystallization quality of the aluminum nitride film in a face-to-face annealing mode, preparing a metal interdigital electrode on the aluminum nitride film in a magnetron sputtering or electron beam evaporation mode, and finally obtaining the aluminum nitride solar blind photodetector. The aluminum nitride detector prepared by the invention has higher response to solar blind band light with the wavelength less than 210nm, the photocurrent of the detector under 50V bias voltage reaches 291nA, and the responsivity is 0.51A/W. The method has the advantages of simple process flow, low cost and suitability for batch production, and the prepared aluminum nitride detector can be applied to the field of solar blind photoelectric detection.

Description

A kind of aluminum nitride solar blind photodetector and preparation method thereof

technical field

The invention belongs to the technical field of semiconductor photoelectric detection, in particular to an aluminum nitride solar blind photoelectric detector and a preparation method thereof.

Background technique

In the process of sunlight hitting the earth, deep ultraviolet light with a wavelength less than 280nm is almost completely absorbed by the atmosphere and cannot reach the earth's surface, so it is called the solar blind zone. Since the sunlight reaching the ground has little interference to the solar blind detection, the solar blind detector can work around the clock and has a very high signal-to-noise ratio. It is widely used in many fields, such as missile tail flame warning, flame control detection, ultraviolet communication, etc. At present, there are not many photodetectors working in the solar blind zone band, and the fabrication cost is very high, making it impossible for mass production and large-scale application.

As the third-generation ultra-wide band gap semiconductor material, aluminum nitride has a band gap of about 6.2 eV, a large absorption coefficient, and a theoretical cut-off wavelength of about 200 nm, which is suitable for the detection of solar-blind band light. At present, the methods that can grow high-quality aluminum nitride materials mainly include: metal organic chemical vapor deposition (MOCVD), physical vapor transport, molecular beam epitaxy and so on. The research group of Professor Hongxing Jiang from Texas Tech University used trimethyl aluminum and ammonia gas as sources to grow aluminum nitride materials with a cut-off wavelength of about 207nm by MOCVD method, and prepared aluminum nitride solar-blind photovoltaics. A detector with a responsivity of about 0.4A/W under 100V bias (Li J, Fan Z Y, Dahal R, et al. 200nm deep ultraviolet photodetectors based on AlN[J]. Applied Physics Letters, 2006, 89 (21 ):213510). However, the MOCVD equipment is very expensive, and the growth temperature of aluminum nitride is high. The general MOCVD system generally cannot meet the growth temperature requirements of aluminum nitride. The equipment needs to be specially modified, and the preparation process is relatively complicated.

In order to reduce the cost of preparing aluminum nitride detectors, the aluminum nitride growth equipment and raw materials used should be as economical and cheap as possible, and the process flow for preparing detectors should be as simple as possible, and at the same time, the devices should have high responsivity. Suitable for mass production.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an aluminum nitride solar-blind photodetector with low cost, easy operation, safety, reliability and high responsivity and a preparation method thereof. This method uses low-cost high-purity aluminum target and high-purity nitrogen as sources, uses reactive RF magnetron sputtering to grow aluminum nitride films on c-plane sapphire substrates, and then improves nitrogen by high-temperature "face-to-face" annealing. The crystalline quality of the aluminum thin film is finally prepared by magnetron sputtering or electron beam evaporation.

As shown in Figure 4, the aluminum nitride solar blind photodetector according to the present invention is composed of a c-plane sapphire substrate, a high-quality aluminum nitride film and metal interdigitated electrodes.

The preparation method of the aluminum nitride solar-blind photodetector of the present invention comprises the following steps:

(1) Use acetone, ethanol, deionized water to ultrasonically clean the c-plane sapphire substrate in turn, and then dry it with high-purity nitrogen for use;

(2) On the c-plane sapphire substrate obtained in step (1), use the reactive radio frequency magnetron sputtering method to grow an aluminum nitride film for 60 to 120 minutes. The gas is high-purity nitrogen (purity is greater than or equal to 99.999%), the sputtering pressure is 0.3-0.5Pa, the radio frequency power is 225-250W, and the sputtering temperature is 350-450°C, and the thickness of the obtained aluminum nitride film is 300-600nm ;

(3) "face-to-face" thermal annealing is performed on the aluminum nitride film prepared in step (2), the annealing temperature is 1500-1600°C, the annealing atmosphere is high-purity nitrogen (purity greater than or equal to 99.999%), and the annealing time is 60-120min ; The "face-to-face" thermal annealing treatment is to cut the aluminum nitride film prepared in step (2) together with the substrate into two halves, and attach the side with the aluminum nitride film to "face-to-face" and press it tightly. , make the aluminum nitride film more closely contact, and then perform high temperature annealing;

(4) depositing a metal layer such as gold, aluminum, titanium, silver, molybdenum, chromium or nickel on the aluminum nitride film annealed in step (3) by magnetron sputtering or electron beam evaporation, and the thickness is 100~ 400nm, and then use the photolithography process to prepare interdigital electrodes, and the finger width and the finger spacing are both 5-100 μm, thereby preparing the aluminum nitride solar-blind photodetector.

The advantages of the present invention are: (1) the technological process is simple, and the cost of the instruments and equipment, material sources and substrates used in the experiment are all low; (2) large-area, high-quality aluminum nitride films can be obtained, which can be applied to Mass production of detectors; (3) The prepared aluminum nitride solar-blind photodetector has high responsivity, fast response speed and good switching repeatability.

Principles of the present invention: (1) Principle of in-situ growth of aluminum nitride films: nitrogen in the chamber is ionized into nitrogen ions and electrons by a strong electric field, and electrons move like cycloids under the combined action of the electric field and the magnetic field, and It collides with other nitrogen atoms to ionize new nitrogen ions and secondary electrons. The nitrogen ions are accelerated by the electric field and shoot towards the aluminum target and bombard the aluminum target. The high-energy aluminum particles escape from the surface of the target and react with nitrogen to form nitridation. Aluminum is attached to the sapphire substrate; (2) "face-to-face" annealing principle of aluminum nitride film: aluminum nitride material is easily decomposed at high temperature, and the "face-to-face" annealing method can inhibit the annealing of aluminum nitride at high temperature. Decompose and recrystallize the grains in the film, eliminate defects and grain boundaries, and significantly improve the crystalline quality of the film; (3) The working principle of aluminum nitride solar-blind photodetectors: when the wavelength is less than the cut-off wavelength of aluminum nitride When deep ultraviolet light is irradiated on the surface of the detector, electrons in aluminum nitride will transition from the valence band to the conduction band, generating a large number of electron-hole pairs, which are separated under the action of external bias and collected by the electrodes on both sides, resulting in photocurrent.

Description of drawings

Fig. 1: the principle schematic diagram of using reactive radio frequency magnetron sputtering to grow aluminum nitride film in the method of the present invention;

Figure 2: Schematic diagram of the process of "face-to-face" annealing of the aluminum nitride film in the method of the present invention;

Figure 3: Raman spectrum (Figure a) and XRD pattern (Figure b) of the aluminum nitride film prepared in step (3) of Example 1;

Figure 4: Schematic diagram of the structure of the aluminum nitride solar-blind photodetector prepared in Example 1;

Figure 5: UV absorption spectrum of the aluminum nitride film prepared in step (3) of Example 1;

Figure 6: I-V characteristic curve (a) and switching characteristic curve (b) of the aluminum nitride solar-blind photodetector prepared in Example 1.

Detailed ways

Example 1

(1) Select c-plane sapphire as the substrate material, first ultrasonically clean the substrate in acetone for 10 min to remove organic matter on the surface, then ultrasonically clean in absolute ethanol for 10 min to remove acetone, and then ultrasonically clean in deionized water for 10 min to remove ethanol , and finally blow dry with high-purity nitrogen.

(2) As shown in Figure 1, fix the aluminum target (purity 99.9995%) on the target base of the radio frequency magnetron sputtering apparatus connected to the cathode, and then fix the c-plane sapphire substrate cleaned in step (1) on the On the sample holder connected to the anode above the aluminum target, the sample was blocked by a baffle, and the target distance between the aluminum target and the sapphire substrate was adjusted to 6 cm. The background vacuum in the growth chamber was pumped to 5.0×10 ^-4 Pa by mechanical pump and molecular pump. Then, 60 sccm of nitrogen gas (purity 99.9995%) was introduced into the growth chamber, and the pressure in the growth chamber was adjusted to 1 Pa. Turn on the RF source, the default sputtering power is 75W, in the auto-tuning mode, click the start button to start the ignition. After the glow was stable, the sputtering power was adjusted to 250W, the pressure in the growth chamber was reduced to 0.3Pa, the substrate heating power was turned on, and the heating temperature was set to 400°C. After 30 min of pre-sputtering, the substrate rotation was turned on, the substrate rotation speed was 10 rps, the baffle was removed, and the formal sputtering was started. The formal sputtering time was 120 min. After the substrate is automatically cooled, the sample is taken out to obtain an aluminum nitride film with a thickness of about 600 nm.

(3) Cut the aluminum nitride film obtained in step (2) together with the substrate into two halves, as shown in FIG. 2, and place the surface on which the aluminum nitride film is grown “face to face” closely together on the graphite On the stage, the sapphire substrate was pressed with a small graphite block to bring the aluminum nitride film into closer contact, and then placed in the chamber of the annealing furnace. Use a mechanical pump and a Roots pump to pump the background vacuum in the chamber to 1Pa, and then introduce high-purity nitrogen (purity above 99.999%) with a flow rate of 200sccm into the chamber to maintain the chamber pressure at about 200Pa. The annealing furnace is heated by means of eddy current generated by the induction coil, and the real-time temperature is calibrated and feedback adjusted by the infrared rays emitted by the infrared temperature probe. The temperature in the chamber of the annealing furnace was raised to 1600°C and maintained for 120 minutes, and then the samples were taken out after voltage cooling and automatic cooling, and high-quality aluminum nitride films were obtained on the sapphire substrate. Its Raman spectrum is shown in Fig. 3(a), the E ₂ (high) vibrational peak is located at 661.9 cm ^-1 , and the half-peak width is only 7.5 cm ^-1 . Its XRD pattern is shown in Figure 3(b), the 2θ diffraction peak of the (0002) crystal plane is located at 36.05°, and the half-peak width is only 0.17°. The UV-Vis absorption spectrum of the film is shown in Fig. 5, and the cut-off wavelength is about 205 nm.

(4) Using electron beam evaporation to deposit a layer of metal aluminum with a thickness of about 300 nm on the aluminum nitride film obtained in step (3), using a photolithography process to prepare interdigital electrodes, the interdigital width and interdigital spacing are both 100 μm, and finally The aluminum nitride solar-blind photodetector is obtained.

(5) Using a light source with a wavelength of 189.4 nm to test the aluminum nitride solar-blind photodetector obtained in step (4), as shown in Figure 6, its photocurrent under 50V bias voltage is as high as 291nA, and the responsivity is 0.51 A/W, with very good switching repeatability, its rise time and fall time are 243ms and 115ms respectively.

Claims (6)

1. a preparation method of aluminum nitride solar-blind photodetector, the steps are as follows: (1) Use acetone, ethanol and deionized water to ultrasonically clean the c-plane sapphire substrate successively, and then dry it with high-purity nitrogen; (2) On the c-plane sapphire substrate obtained in step (1), an aluminum nitride film is grown by a reactive radio frequency magnetron sputtering method for 60-120 minutes. The aluminum source is a high-purity aluminum target, and the working gas is high-purity nitrogen. The jet pressure is 0.3～0.5Pa, the radio frequency power is 225～250W, the sputtering temperature is 350～450℃, and the thickness of the obtained aluminum nitride film is 300～600nm; (3) "face-to-face" thermal annealing is performed on the aluminum nitride film prepared in step (2), the annealing temperature is 1500-1600°C, the annealing atmosphere is high-purity nitrogen (purity greater than or equal to 99.999%), and the annealing time is 60-120min ; (4) depositing a metal layer such as gold, aluminum, titanium, silver, molybdenum, chromium or nickel on the aluminum nitride film annealed in step (3) by magnetron sputtering or electron beam evaporation, and the thickness is 100~ 400nm, and then use a photolithography process to prepare interdigital electrodes, and the finger width and the finger spacing are both 5-100 μm, thereby preparing the aluminum nitride solar-blind photodetector. 2 . The method for preparing an aluminum nitride solar-blind photodetector according to claim 1 , wherein the aluminum nitride film is prepared by a reactive radio frequency magnetron sputtering method. 3 . 3 . The method for preparing an aluminum nitride solar-blind photodetector according to claim 1 , wherein the purity of the high-purity nitrogen gas is more than 99.999%. 4 . 4 . The method for preparing an aluminum nitride solar-blind photodetector according to claim 1 , wherein the purity of the high-purity aluminum target material is more than 99.95%. 5 . 5. the preparation method of a kind of aluminum nitride solar blind photodetector as claimed in claim 1 is characterized in that: "face-to-face" thermal annealing treatment is to cut the aluminum nitride film prepared in step (2) together with the substrate into The two halves, the sides on which the aluminum nitride film is grown are "face-to-face" and pressed together to make the aluminum nitride film more closely contact, and then annealed. 6. An aluminum nitride solar-blind photodetector, characterized in that: it is prepared by the method of any one of claims 1-5.

Images