CN116154019A - Solar blind ultraviolet detector with improved diamond Schottky junction interface of oxide dielectric layer and preparation method thereof - Google Patents

Abstract

A solar-blind ultraviolet detector with a diamond Schottky junction interface improved by an oxide dielectric layer and a preparation method thereof, the invention aims to solve the problems of high operating voltage, low responsivity and low detectability of existing solar-blind ultraviolet detectors. The solar-blind ultraviolet detector of the present invention deposits a diamond intrinsic layer on the upper surface of the boron-doped diamond substrate, deposits a metal film layer on the lower surface of the boron-doped diamond substrate as an ohmic electrode, and deposits an oxide layer on the upper surface of the diamond intrinsic layer. A material dielectric layer, on which a metal electrode is deposited as a Schottky electrode; wherein the oxide dielectric layer is TiO ₂ , ZrO ₂ , Al ₂ O ₃ or SiO ₂ . The diamond Schottky junction of the oxide-improved diamond Schottky junction interface of the present invention has a higher turn-on voltage, and after ultraviolet light is applied, the light makes the device turn on in advance, thereby obtaining a high photocurrent response. At the same time, it has high photocurrent response and low dark current, which ensures the high detectability of the device.

Description

Solar-blind UV detector with modified diamond Schottky junction interface by oxide dielectric layer and its preparation method

technical field

The invention belongs to the field of photoelectric detection of semiconductor devices, in particular to a high-performance sun-blind ultraviolet detection device with an oxide-improved diamond Schottky junction interface and a preparation method thereof.

Background technique

Ultraviolet rays with a wavelength of less than 280nm are called solar blind ultraviolet rays. The ultraviolet rays in this range of the solar spectrum interact strongly with the atmosphere and are mostly absorbed by the atmosphere. Therefore, the sunlight on the surface of the earth contains very little radiation in this band, which provides a natural low-radiation environment for detectors in this band. . Diamond is a wide bandgap semiconductor material. It has a bandgap width of 5.5eV and is suitable for making solar-blind ultraviolet detection devices. Diamond sun-blind UV devices with various structures have been developed. There are mainly photoconductive and junction structures. The photoconductive type is mainly made of non-doped intrinsic diamond (IIa), and the carriers excited by ultraviolet light are collected by applying a high external bias voltage to form a photocurrent. The junction devices mainly include diamond Schottky junction, diamond PIN junction and heterojunction composed of diamond and other semiconductor materials. Such devices can operate at lower voltages due to the built-in potential barrier of the device itself. Responsivity is the ratio of device photocurrent to incident light power, and is an important index reflecting device performance. However, the responsivity does not take into account the effect of the dark current of the device. In practical applications, it is always desired that the greater the responsivity of the device, the better the dark current, and the lower the operating voltage. The detectability takes into account both the device responsivity and the influence of dark current. Therefore, a detection device with better performance should have greater responsivity, detectability and lower operating voltage.

Contents of the invention

The purpose of the present invention is to solve the problems of high working voltage, low responsivity and low detectability of existing solar-blind ultraviolet detection devices, and to provide a low working voltage with high responsivity and high detectability High-degree diamond solar-blind ultraviolet detection device and its preparation method.

The sun-blind ultraviolet detector of the diamond Schottky junction interface improved by the oxide dielectric layer of the present invention comprises an ohmic contact electrode, a boron-doped diamond substrate, a diamond intrinsic epitaxial layer, an oxide dielectric layer and a Schottky electrode, and the boron-doped A diamond intrinsic layer is deposited on the upper surface of the diamond substrate, a metal film layer is deposited on the lower surface of the boron-doped diamond substrate as an ohmic electrode, an oxide dielectric layer is deposited on the upper surface of the diamond intrinsic layer, and on the oxide dielectric layer A (thin) metal electrode is deposited as a Schottky electrode; wherein the oxide dielectric layer is a stacked film formed by one or more of TiO ₂ , ZrO ₂ , Al ₂ O ₃ , SiO ₂ , AlN, and SiN.

The oxide dielectric layer used in the present invention is a non-conductive thin film and does not provide carriers. It has a passivation effect on Schottky interface defects and interface states, and suppresses the inhomogeneity of the interface barrier, thereby adjusting the turn-on voltage range. .

The preparation method of the sun-blind ultraviolet detector of the diamond Schottky junction interface improved by the oxide dielectric layer of the present invention is realized according to the following steps:

1. Using microwave plasma chemical vapor deposition method to epitaxially grow the diamond intrinsic layer on the boron-doped diamond substrate to obtain the diamond substrate;

2. Carry out heat treatment to the diamond substrate at 450-590°C in air to obtain a heat-treated diamond substrate;

3. Deposit ohmic contact electrodes on the boron-doped diamond first measurement of the heat-treated diamond substrate, and obtain the annealed diamond substrate after annealing treatment;

4. Depositing an oxide dielectric layer on one side of the diamond intrinsic epitaxial layer of the annealed diamond substrate to obtain a diamond substrate with an oxide dielectric layer;

5. Depositing a metal Schottky electrode on the upper surface of the diamond substrate with an oxide medium layer to obtain a sun-blind ultraviolet detector with an oxide-improved diamond Schottky junction interface.

The high-performance solar-blind ultraviolet detector of the oxide-improved diamond Schottky junction interface of the present invention and its preparation method include the following beneficial effects:

The oxide-improved diamond Schottky junction has a higher Schottky barrier and turn-on voltage, that is, a dark current without light, and requires a higher forward voltage to have a larger forward conduction current. However, ordinary diamond Schottky junction devices usually have lower Schottky barrier and turn-on voltage due to factors such as the barrier inhomogeneity on the diamond surface. This makes the device dark current higher at lower forward voltages, making it impossible to guarantee good detectability. The diamond Schottky junction of the oxide-improved diamond Schottky junction interface of the present invention has a higher turn-on voltage, which means that under a certain forward voltage, the dark current is low; after applying ultraviolet light, the light makes the device advance turned on, resulting in a high photocurrent response. Therefore, it has high photocurrent response and low dark current at the same time, thereby ensuring the high detectability of the device. In addition, since the device is based on a diamond Schottky junction, it can also work at 0V, which can be used as a self-powered detection device.

Description of drawings

Fig. 1 is the structural representation of the sun-blind ultraviolet detector of the improved diamond Schottky junction interface of the oxide of the present invention;

代表240nm，/>

代表250nm，六边形代表260nm，☆代表280nm，五边形代表300nm，圆中带点代表320nm，+代表360nm，×代表400nm，*代表440nm，－代表480nm，∣代表520nm；Fig. 2 is the dark current of the sun-blind ultraviolet detector in the embodiment and the photocurrent test diagram under the irradiation of different ultraviolet wavelengths, wherein □ represents darkness, ○ represents 200nm, △ represents 210nm, ▽ represents 220nm, ◇ represents 230nm,

stands for 240nm, />

Represents 250nm, hexagon represents 260nm, ☆ represents 280nm, pentagon represents 300nm, dot in the circle represents 320nm, + represents 360nm, × represents 400nm, * represents 440nm, - represents 480nm, ∣ represents 520nm;

Fig. 3 is the responsivity test diagram under different wavelengths of the sun-blind ultraviolet detector in the embodiment, wherein □ represents -2.8V, ○ represents -1V, △ represents 0V, and ▽ represents 1V;

Fig. 4 is the detectability test chart of different wavelengths of the sun-blind ultraviolet detector in the embodiment, wherein □ represents -2.8V, ○ represents -1V, △ represents 0V, and ▽ represents 1V;

Fig. 5 is a test chart of signal-to-noise ratio at different wavelengths of the solar-blind ultraviolet detector in the embodiment, wherein □ represents -2.8V, ○ represents -1V, △ represents 0V, and ▽ represents 1V.

Detailed ways

Embodiment 1: The solar-blind ultraviolet detector of the oxide-improved diamond Schottky junction interface in this embodiment includes an ohmic contact electrode 1, a boron-doped diamond substrate 2, a diamond intrinsic epitaxial layer 3, an oxide dielectric layer 4 and The Schottky electrode 5 is deposited with a diamond intrinsic layer 3 on the upper surface of the boron-doped diamond substrate 2, and a metal film layer is deposited on the lower surface of the boron-doped diamond substrate 2 as an ohmic electrode 1, and on the diamond intrinsic layer 3 An oxide dielectric layer 4 is deposited on the upper surface, and a (thin) metal electrode is deposited on the oxide layer 4 as a Schottky electrode 5; wherein the oxide dielectric layer 4 is TiO ₂ , ZrO ₂ , Al ₂ O ₃ , SiO ₂ , AlN , SiN or one or more forms a stacked film.

In this embodiment, the oxide dielectric layer adjusts the device structure of the Schottky interface. Unlike other heterojunction devices, the oxide dielectric layer does not provide carriers, but only changes the interface energy band structure, so the device is unipolar. device without degrading the response speed of the detection device.

The high-performance solar-blind ultraviolet detection device of the oxide-improved diamond Schottky junction interface described in this embodiment can work at -3 and 0V, and has excellent responsivity.

Specific embodiment two: the difference between this embodiment and specific embodiment one is that the material of Schottky electrode 5 is one of Au, Pt, Ru, Pd, W, Cu, Rh, Mo, Pb, Ir, W or A variety of laminated films are formed.

Embodiment 3: This embodiment differs from Embodiment 2 in that the thickness of the Schottky electrode 5 is between 5 nm and 30 nm.

Embodiment 4: This embodiment differs from Embodiments 1 to 3 in that the thickness of the oxide dielectric layer 4 is 5-100 nm.

Embodiment 5: This embodiment differs from Embodiment 1 to Embodiment 4 in that the ohmic contact electrode 1 is Au, Pt, Ru, Pd, Ru, Ti/Au, Ti/Pt/Au, Ti/Ru, Ti/ One or more of Mo, Cr/Au, Cr/Ru, W, Cu, Rh, Mo, Pb, Ir, and W forms a laminated film.

In this embodiment, the thickness of the ohmic contact electrode 1 is between 5 nm and 1000 nm.

Specific embodiment six: the preparation method of the sun-blind ultraviolet detector of the oxide-improved diamond Schottky junction interface in this embodiment is implemented according to the following steps:

1. Using microwave plasma chemical vapor deposition method to epitaxially grow the diamond intrinsic layer on the boron-doped diamond substrate to obtain the diamond substrate;

2. Carry out heat treatment to the diamond substrate at 450-590°C in air to obtain a heat-treated diamond substrate;

3. Deposit ohmic contact electrodes on the boron-doped diamond first measurement of the heat-treated diamond substrate, and obtain the annealed diamond substrate after annealing treatment;

4. Depositing an oxide dielectric layer on one side of the diamond intrinsic epitaxial layer of the annealed diamond substrate to obtain a diamond substrate with an oxide dielectric layer;

5. Depositing a metal Schottky electrode on the upper surface of the diamond substrate with an oxide medium layer to obtain a sun-blind ultraviolet detector with an oxide-improved diamond Schottky junction interface.

Specific embodiment seven: the difference between this embodiment and specific embodiment six is that the process of epitaxially growing the diamond intrinsic layer on the boron-doped diamond substrate is as follows:

Place the boron-doped diamond substrate in the cabin of a microwave plasma chemical vapor deposition device, vacuumize the cabin (vacuum degree is 10 ^-7 ~ 10 ^-5 mbar), control the flow rate of hydrogen to 160 ~ 200 sccm, turn on the microwave power, Gradually increase the gas pressure and microwave power to make the boron-doped diamond substrate grow at a temperature of 600-1100°C, feed CH ₄ , and control the flow rate of CH ₄ to 4-8 sccm to epitaxially grow the diamond intrinsic layer.

Embodiment 8: This embodiment differs from Embodiment 7 in that the thickness of the epitaxially grown diamond intrinsic layer is between 0.5 μm and 20 μm.

Embodiment 9: This embodiment is different from Embodiment 6 to Embodiment 8 in that the heat treatment process in step 2 is replaced by: putting the diamond substrate into a hot mixed acid solution (HNO ₃ : H ₂ SO ₄ =1:1 ) to 200-400°C for 30-240 minutes, and ultrasonically cleaned in acetone, deionized water, and acetone solution in sequence.

Embodiment 10: This embodiment is different from Embodiment 6 to Embodiment 9 in that the annealing treatment described in Step 3 is annealing at 450° C. for 10 to 30 minutes.

In this embodiment, the annealing treatment is used to improve the contact characteristics.

Embodiment 11: This embodiment is different from Embodiment 6 to Embodiment 11 in that the deposition described in Step 3, Step 4 and Step 5 is deposited by magnetron sputtering, thermal evaporation or electron beam evaporation.

Embodiment: The preparation method of the solar-blind ultraviolet detector of the oxide-improved diamond Schottky junction interface in this embodiment is implemented according to the following steps:

1. Put the boron-doped diamond substrate in the microwave plasma chemical vapor deposition system, evacuate the cabin, and the vacuum degree reaches 5×10 ^-6 mbar, inject hydrogen gas, the flow rate is 194 sccm, turn on the microwave power supply, and alternately increase the air pressure With microwave power, the temperature of the boron-doped diamond substrate reaches 800°C, and CH ₄ is introduced, and the flow rate of CH ₄ is controlled to 6 sccm to carry out epitaxial growth of the diamond intrinsic layer. The carbon groups are exhausted, slowly lower the temperature, and reduce the pressure. When the pressure in the cabin drops below 10 ^-3 mbar, open the cabin to obtain a diamond substrate;

2. Put the diamond substrate into a hot mixed acid solution (HNO ₃ and H ₂ SO ₄ volume ratio is 1:1) and heat it at 350°C, clean it, and then perform ultrasonic cleaning in acetone, deionized water, and acetone solution in turn , to obtain the cleaned diamond substrate;

3. The first measurement of boron-doped diamond on the cleaned diamond substrate uses magnetron sputtering to deposit Ti/Au metal ohmic contact electrodes. The deposition pressure is 0.5Pa, the power of the radio frequency source is 60W and 40W, and the deposition time is 3 and 4min. , and annealed at 450°C for 15 minutes to improve the contact characteristics, and an annealed diamond substrate was obtained;

4. On the side of the diamond intrinsic epitaxial layer of the diamond substrate after annealing, a titanium oxide layer is deposited by radio frequency magnetron sputtering. The target material is a high-purity titanium target. The flow rates of argon and oxygen are 20 sccm and 5 sccm respectively, and the air pressure is 1 Pa. The deposition thickness is 10nm to obtain a diamond substrate with an oxide dielectric layer;

5. Deposit a metal Schottky electrode on the upper surface of the diamond substrate with an oxide dielectric layer by magnetron sputtering. The deposition target is a high-purity gold target, the air pressure is 0.5Pa, the power is 40W, and the thickness is about 10nm. Sun-blind UV detectors at the interface of diamond Schottky junctions modified by materials.

Fig. 2 is a curve of the dark current of the oxide-improved diamond Schottky junction detection device and the photocurrent of the device under different ultraviolet wavelengths. It can be seen that in the range of -2.8 to 2V (the metal ohmic contact electrode is grounded), the device maintains a low current level, and after applying monochromatic ultraviolet light, the current increases significantly, and at 0V There is still a high photocurrent under the bias voltage, showing obvious self-supply characteristics. Under forward bias, the dark current of the device shows an obvious upward trend after -2.8V, while the rapid rise of the photocurrent occurs after about -1.5V, which means that the device remains low at -2.8V. The dark current level is low, but the light makes the device turn on in advance at a voltage lower than -2.8V, and enters the stage where the current increases rapidly with the forward bias voltage (negative bias voltage), and obtains a large photocurrent response. This is mainly due to the introduction of the titanium dioxide layer, which regulates the dark current of the device.

Figure 3 shows the responsivity curves of the device at 1, 0, -1 and -2.8V. The responsivity is the ratio of the photocurrent of the device to the power of the incident ultraviolet light, which is an important index to measure the detection performance of the device. When the working voltage is only -2.8V, the responsivity of the device reaches 1156.1mA/W under the irradiation of 220nm ultraviolet light, which shows that the device can obtain high ultraviolet light response under low voltage. The ratio of device UV responsivity to visible light responsivity is also called UV/visible light attenuation rate, which can be used to characterize the sun-blind UV characteristics of the device. The ultraviolet/visible light attenuation rate of the device fabricated in this embodiment is measured by the ratio of the ultraviolet light responsivity of 220nm and 480nm under the bias voltage of -2.8 and 0V, which can be respectively 40286.4 and 18132.8. This means that the device has good solar-blind UV characteristics.

Under 0V bias, the responsivity of the device reaches 5.6mA/W under the irradiation of 220nm ultraviolet light, which means that the device has good self-power supply characteristics. It can work without external bias voltage.

In order to further measure the comprehensive performance of the device, the index of detectability is introduced, and the influence of device responsivity and dark current is considered at the same time. Figure 4 shows the detectability of the device. When the operating voltage is only -2.8V, the detectability of the device is as high as 8.7×10 ¹³ Jones under the irradiation of 220nm ultraviolet light.

The signal-to-noise ratio can be used to measure the sensitivity of the device. Figure 5 shows the signal-to-noise ratio of the device at different wavelengths. When the working voltage is only -2.8V, under the irradiation of 220nm ultraviolet light, the signal-to-noise ratio of the device is as high as 68366.5, which shows its high sensitivity.

In summary, the oxide-improved diamond Schottky junction detection device of the present invention can work without an external bias voltage, and has good self-power supply performance and solar-blind ultraviolet characteristics; when the operating voltage is only -2.8V, Under the irradiation of 220nm ultraviolet light, its responsivity reaches 1156.1mA/W, its detectability is as high as 8.7×10 ¹³ Jones, and its signal-to-noise ratio is as high as 68366.5. It has excellent ultraviolet detection ability.

Claims (10)

1. The solar blind ultraviolet detector of the diamond Schottky junction interface with the improved oxide dielectric layer is characterized by comprising an ohmic contact electrode (1), a boron-doped diamond substrate (2), a diamond intrinsic epitaxial layer (3), an oxide dielectric layer (4) and a Schottky electrode (5), wherein the diamond intrinsic layer (3) is deposited on the upper surface of the boron-doped diamond substrate (2), a metal film layer is deposited on the lower surface of the boron-doped diamond substrate (2) to serve as the ohmic electrode (1), the oxide dielectric layer (4) is deposited on the upper surface of the diamond intrinsic layer (3), and the metal electrode is deposited on the oxide dielectric layer (4) to serve as the Schottky electrode (5); wherein the oxide dielectric layer (4) is TiO ₂ 、ZrO ₂ 、Al ₂ O ₃ 、SiO ₂ A laminated film formed of one or more of AlN and SiN.

2. The solar blind ultraviolet detector with the improved diamond schottky junction interface of the oxide dielectric layer according to claim 1, wherein the schottky electrode (5) is made of one or more of Au, pt, ru, pd, W, cu, rh, mo, pb, ir, W materials to form a laminated film.

3. An improved diamond schottky junction interface solar blind uv detector according to claim 1, characterized in that the schottky electrode (5) has a thickness between 5 and 30 nm.

4. The solar blind ultraviolet detector of the diamond schottky junction interface modified by the oxide dielectric layer according to claim 1, wherein the thickness of the oxide dielectric layer (4) is 5-100 nm.

5. The solar blind ultraviolet detector with the improved diamond Schottky junction interface by the oxide dielectric layer according to claim 1, wherein the ohmic contact electrode (1) is one or more of Au, pt, ru, pd, ru, ti/Au, ti/Pt/Au, ti/Ru, ti/Mo, cr/Au and Cr/Ru, W, cu, rh, mo, pb, ir, W to form a laminated film.

6. The method for preparing an oxide-modified diamond schottky junction interface solar blind ultraviolet detector according to claim 1, wherein the preparation method is realized according to the following steps:

1. epitaxially growing a diamond intrinsic layer on the boron-doped diamond substrate by adopting a microwave plasma chemical vapor deposition method to obtain a diamond substrate;

2. heating the diamond substrate in air at 450-590 ℃ to obtain a heat-treated diamond substrate;

3. depositing an ohmic contact electrode on the boron-doped diamond of the diamond substrate after heat treatment, and annealing to obtain an annealed diamond substrate;

4. depositing an oxide dielectric layer on one side of the annealed diamond intrinsic epitaxial layer of the diamond substrate to obtain the diamond substrate with the oxide dielectric layer;

5. and depositing a metal Schottky electrode on the upper surface of the diamond substrate with the oxide dielectric layer to obtain the solar blind ultraviolet detector with the oxide improved diamond Schottky junction interface.

7. The method of fabricating an oxide-modified diamond schottky junction interface solar blind ultraviolet detector according to claim 6, wherein the epitaxial growth of the intrinsic layer of diamond on the boron-doped diamond substrate is performed as follows:

placing the boron-doped diamond substrate in a cabin of a microwave plasma chemical vapor deposition device, vacuumizing the cabin, controlling the hydrogen flow to be 160-200 sccm, starting a microwave power supply, gradually increasing the air pressure and the microwave power to ensure that the growth temperature of the boron-doped diamond substrate is 600-1100 ℃, and introducing CH ₄ Control CH ₄ And epitaxially growing the diamond intrinsic layer at a flow rate of 4-8 sccm.

8. The method of fabricating an oxide-modified diamond schottky junction interface solar blind ultraviolet detector according to claim 6, wherein the thickness of the epitaxially grown diamond intrinsic layer is between 0.5 and 20 μm.

9. The method of fabricating an oxide-modified diamond Schottky junction interface solar blind ultraviolet detector as recited in claim 6, wherein said annealing in step three is performed at 450 ℃ for 10-30 minutes.

10. The method of fabricating an oxide-modified diamond Schottky junction interface solar blind ultraviolet detector as recited in claim 6, wherein the deposition in step three, step four and step five is performed by magnetron sputtering, thermal evaporation or electron beam evaporation.

Images