Diamond / gallium oxide ultraviolet detector and preparation method thereof

Abstract

The invention discloses a diamond / gallium oxide ultraviolet detector and a preparation method thereof. The diamond / gallium oxide ultraviolet detector sequentially comprises a single crystal diamond substrate, an intrinsic single crystal diamond epitaxial layer, an finger-type ohmic electrode, a gallium oxide layer and a finger-type Schottky electrode from bottom to top, the finger-type ohmic electrode comprises an ohmic electrode strip array and an ohmic electrode pad which are connected with each other; the finger-type Schottky electrode comprises a Schottky electrode strip array and a Schottky electrode pad which are connected with each other; and the ohmic electrode strip array and the Schottky electrode strip array form a different-plane interdigital structure. Defects formed by the diamond layer and the gallium oxide layer are depleted, capture or recombination of interface defects to photon-generated carriers is reduced, electric field distribution can be optimized, collection of the carriers is facilitated, and the performance of the device is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of semiconductor applications, and particularly relates to a diamond / gallium oxide ultraviolet detector and a preparation method thereof. BACKGROUND

[0002] Solar blind ultraviolet photodetectors have important values in military and civilian fields, and have attracted extensive attention of researchers in recent years. Gallium oxide has an ultra-wide band gap (4.8-4.9 eV), and is one of ideal materials for preparing solar blind ultraviolet photodetectors. However, the thermal conductivity of gallium oxide is low, which leads to problems in heat dissipation. In comparison, diamond has high thermal conductivity, high electron mobility and large band gap, and can solve the problem of limited light detection performance in harsh environments such as high temperature. The combination of diamond and gallium oxide can improve the overall responsivity of the device in the solar blind range, and increase the reliability of the device.

[0003] The common method for preparing a diamond / gallium oxide composite structure detector at present is to deposit a gallium oxide film on the surface of a single crystal diamond, and then prepare an interdigital structure electrode on the gallium oxide film to form a detector. However, due to the large lattice mismatch between gallium oxide and diamond, a single crystal film cannot be obtained, and many defects exist in the diamond / gallium oxide interface, which are concentrated on the side of the gallium oxide material. These defects can trap photo-generated carriers, which reduces the carrier collection efficiency and thus the responsivity, and also slows down the response speed. SUMMARY

[0004] The purpose of the present application is to provide a diamond / gallium oxide ultraviolet detector, which adopts an out-of-plane single Schottky electrode structure to achieve high responsivity and high response speed. The second purpose of the present application is to provide a preparation method of the diamond / gallium oxide ultraviolet detector.

[0005] Technical scheme: The diamond / gallium oxide ultraviolet detector provided by the present application comprises, from bottom to top, a single crystal diamond substrate, an intrinsic single crystal diamond epitaxial layer, a finger-shaped ohmic electrode, a gallium oxide layer, and a finger-shaped Schottky electrode. The finger-shaped ohmic electrode comprises an array of ohmic electrode strips and an ohmic electrode pad connected thereto. The finger-shaped Schottky electrode comprises an array of Schottky electrode strips and a Schottky electrode pad connected thereto. The array of ohmic electrode strips and the array of Schottky electrode strips form an out-of-plane interdigital structure.

[0006] The array of ohmic electrode strips is arranged on the intrinsic diamond epitaxial layer. The gallium oxide layer is arranged on the entire ohmic electrode array region and part of the ohmic electrode pad region. The array of Schottky electrode strips is arranged on the gallium oxide layer and forms an out-of-plane interdigital structure with the array of ohmic electrode strips. The ohmic electrode pad and the array of ohmic electrode strips are an integral whole prepared at the same time, and the Schottky electrode pad and the array of Schottky electrode strips are an integral whole prepared at the same time.

[0007] Preferably, the intrinsic single crystal diamond epitaxial layer has a thickness of 100-1000 nm, an impurity concentration of less than 1 ppm, and a defect density of less than 10 6 cm -2 .

[0008] Preferably, the finger-shaped ohmic electrode material is one or more of W, Ti, and Al, and has a thickness of 30-200 nm; the electrode strip width of the ohmic electrode strip array is 5-20 μm.

[0009] Preferably, the gallium oxide layer has a thickness of 50-220 nm, and the thickness is at least 20 nm greater than the thickness of the finger-shaped ohmic electrode.

[0010] Preferably, the finger-shaped Schottky electrode material is one or more of Au, Ni, and Pt, and has a thickness of 20-200 nm; the electrode strip width of the Schottky electrode strip array is 5-20 μm.

[0011] Preferably, the lateral electrode spacing between the electrode strips of the Schottky electrode strip array and the electrode strips of the ohmic electrode strip array is 10-30 μm.

[0012] The method for preparing the diamond / gallium oxide ultraviolet detector described in the present application comprises the following steps:

[0013] (1) growing an intrinsic single crystal diamond epitaxial layer on a single crystal diamond substrate using MPCVD technology, and converting the surface hydrogen termination into oxygen termination using ultraviolet ozone treatment;

[0014] (2) forming a finger-shaped ohmic electrode on the surface of the intrinsic single crystal diamond epitaxial layer using micro-nano processing technology;

[0015] (3) depositing a gallium oxide layer on the surface of the intrinsic single crystal diamond epitaxial layer and the surface of the finger-shaped ohmic electrode using ALD technology;

[0016] (4) preparing a finger-shaped Schottky electrode on the gallium oxide layer using micro-nano processing technology, and forming an out-of-plane interdigital structure with the finger-shaped ohmic electrode;

[0017] (5) forming a photoresist mask on the gallium oxide layer using standard photolithography technology, and performing windowing on the exposed gallium oxide using an acid solution to expose part of the ohmic electrode pad.

[0018] Preferably, in step (1), the growth pressure of the intrinsic diamond layer is 90-120 Torr, the methane flow rate is 1-5 sccm, the hydrogen flow rate is 400-500 sccm, the temperature is 800-900 °C, and the epitaxial growth rate is 0.1-5 nm / min.

[0019] Preferably, in step (3), the gallium oxide deposition conditions are as follows: the background pressure is 10 -2Pa, the growth temperature is maintained at 200-350℃.

[0020] Preferably, in step (5), the acid solution used for etching is at least one of hydrochloric acid, nitric acid and phosphoric acid.

[0021] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages: the defects formed by the depletion diamond layer and the gallium oxide layer are depleted, the capture or recombination of photo-generated carriers by interface defects is reduced, and the electric field distribution can be optimized, thereby facilitating the collection of carriers and improving the performance of the device. Experimental data show that the performance of the detector prepared by the present application is significantly better than that of the conventional coplanar electrode structure, the photocurrent is increased from 51.9nA to 74.8nA (about 44% increase), the response speed is also increased by an order of magnitude, the rise time is shortened from 0.85s to 0.08s, and the fall time is shortened from 0.64s to 0.05s, thereby realizing high responsivity and high response speed. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a three-dimensional schematic view of the diamond / gallium oxide ultraviolet detector of the present application.

[0023] Figure 2 Fig. 2 is a sectional view of the diamond / gallium oxide ultraviolet detector of the present application.

[0024] Figure 3 Fig. 3 is a performance comparison between the out-of-plane Schottky electrode diamond / gallium oxide ultraviolet detector and the coplanar electrode detector.

[0025] Fig. 1 is a three-dimensional schematic view of the diamond / gallium oxide ultraviolet detector of the present application. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be further described below in combination with the drawings, examples and comparative examples.

[0027] Example 1

[0028] As Figure 1The method for fabricating a diamond / gallium oxide ultraviolet detector is shown. The substrate is a high-quality intrinsic single-crystal diamond substrate 1 of type IIa synthesized by high-temperature and high-pressure method, with a thickness of 100 μm. It is sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 min, and then purged with nitrogen for 20 s. Then, it is placed in an MPCVD apparatus for the growth of an intrinsic diamond epitaxial layer with a thickness of 100 nm, a growth pressure of 90 Torr, a methane flow rate of 1 sccm, a hydrogen flow rate of 400 sccm, a temperature of 800 °C, and an epitaxial growth rate of 0.1 nm / min. Ultraviolet ozone treatment is used to oxidize hydrogen terminals to oxygen terminals. Finger-shaped ohmic electrodes are formed on the surface of the intrinsic diamond epitaxial layer using micro-nano fabrication processes. The electrode strips are 5 μm wide and 30 nm thick. Then, a gallium oxide thin film is deposited on the intrinsic diamond surface and the finger-shaped ohmic electrode surface using ALD technology, with a deposition background pressure of 10... -2 The growth temperature was maintained at 200℃, and the thickness was 50nm. Next, finger-shaped Schottky electrodes were formed on the gallium oxide surface using micro-nano fabrication techniques. The Schottky electrode strips were 5μm wide and 100nm thick, with a lateral spacing of 10μm between them and the ohmic electrode strips. Finally, a photoresist mask was formed on the gallium oxide film using standard photolithography. A hydrochloric acid solution was used to create a window in the exposed gallium oxide, revealing part of the ohmic electrode pad4, thus obtaining the detector.

[0029] Example 2

[0030] like Figure 1 The method for fabricating a diamond / gallium oxide ultraviolet detector is shown. The substrate is a high-quality intrinsic single-crystal diamond substrate 1 of type IIa synthesized by high-temperature and high-pressure method, with a thickness of 100 μm. It is sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 min, and then purged with nitrogen for 20 s. Then, it is placed in an MPCVD apparatus for the growth of an intrinsic diamond epitaxial layer with a thickness of 500 nm, a growth pressure of 100 Torr, a methane flow rate of 3 sccm, a hydrogen flow rate of 450 sccm, a temperature of 850 °C, and an epitaxial growth rate of 2.5 nm / min. Ultraviolet ozone treatment is used to oxidize hydrogen terminals to oxygen terminals. Finger-shaped ohmic electrodes are formed on the surface of the intrinsic diamond epitaxial layer using micro-nano fabrication processes. The ohmic electrode strips are 15 μm wide and 100 nm thick. Then, a gallium oxide thin film is deposited on the intrinsic diamond surface and the finger-shaped ohmic electrode surface using ALD technology, with a deposition background pressure of 10... -2The growth temperature was maintained at 300℃, and the thickness was 150nm. Next, finger-shaped Schottky electrodes were formed on the gallium oxide surface using micro-nano fabrication processes. The Schottky electrode strips were 15μm wide and 150nm thick, with a lateral spacing of 20μm between them and the ohmic electrode strips. Finally, a photoresist mask was formed on the gallium oxide film using standard photolithography. A nitric acid solution was used to create a window in the exposed gallium oxide, revealing part of the ohmic electrode pad4, thus obtaining the detector.

[0031] Example 3

[0032] like Figure 1 The method for fabricating a diamond / gallium oxide ultraviolet detector is shown. The substrate is a high-quality intrinsic single-crystal diamond substrate 1 of type IIa synthesized by high-temperature and high-pressure method, with a thickness of 100 μm. It is sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 min, followed by nitrogen purging for 20 s. Then, it is placed in an MPCVD apparatus for the growth of an intrinsic diamond epitaxial layer with a thickness of 1000 nm, a growth pressure of 120 Torr, a methane flow rate of 5 sccm, a hydrogen flow rate of 500 sccm, a temperature of 900 °C, and an epitaxial growth rate of 5 nm / min. Ultraviolet ozone treatment is used to oxidize hydrogen terminals to oxygen terminals. Finger-shaped ohmic electrodes are formed on the surface of the intrinsic diamond epitaxial layer using micro-nano fabrication processes. The ohmic electrode strips are 20 μm wide and 180 nm thick. Then, a gallium oxide thin film is deposited on the intrinsic diamond surface and the finger-shaped ohmic electrode surface using ALD technology, with a deposition background pressure of 10... -2 The growth temperature was maintained at 350℃, and the thickness was 220nm. Next, finger-shaped Schottky electrodes were formed on the gallium oxide surface using micro-nano fabrication processes. The Schottky electrode strips were 20μm wide and 200nm thick, with a lateral spacing of 30μm between them and the ohmic electrode strips. Finally, a photoresist mask was formed on the gallium oxide film using standard photolithography. A phosphoric acid solution was used to create a window in the exposed gallium oxide, revealing part of the ohmic electrode pad4, thus obtaining the detector.

[0033] Comparative Example 1

[0034] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 is a conventional coplanar electrode diamond / gallium oxide ultraviolet detector, which, from bottom to top, comprises an intrinsic single-crystal diamond substrate, a diamond epitaxial layer, a gallium oxide layer, and a metal electrode. The metal electrode is opaque and has no buried electrode structure. The size parameters of its electrode array are the same as those of the device in Example 1. The fabrication method involves growing an intrinsic diamond epitaxial layer on the surface of the intrinsic single-crystal diamond substrate 1, then treating the surface to oxygen termination, and then depositing a gallium oxide thin film on the intrinsic diamond surface using ALD technology. Subsequently, interdigitated metal electrodes with micro / nano fabrication processes are used to fabricate the detector.

[0035] The performance of the detector of Comparative Example 1 and Example 1 is compared as shown in Table 1. Figure 3 As shown in Table 1, it can be seen that the out-of-plane Schottky electrode diamond / gallium oxide ultraviolet detector of Example 1 has a larger photocurrent and a faster response speed than the traditional coplanar electrode of Comparative Example.

[0036] The detection process is as follows: the sample is placed on the sample stage of the Agilent B1505A test equipment, the voltage is introduced to the surface of the sample by the probe, and the current signal of the device under the light pulse is collected at a fixed voltage. As a result, the out-of-plane Schottky electrode diamond / gallium oxide ultraviolet detector prepared by the present application has a photocurrent of 74.8nA, a rise time of 0.08s and a fall time of 0.05s; the traditional coplanar electrode diamond / gallium oxide ultraviolet detector has a photocurrent of 51.9nA, a rise time of 0.85s and a fall time of 0.64s. The results show that the out-of-plane Schottky electrode diamond / gallium oxide ultraviolet detector of the present application has higher sensitivity and faster response speed.

Claims

1. A diamond / gallium oxide ultraviolet detector, characterized by, The single crystal diamond substrate (1), the intrinsic single crystal diamond epitaxial layer (2), the finger-shaped ohmic electrode, the gallium oxide layer (5), and the finger-shaped Schottky electrode are sequentially arranged from bottom to top; the finger-shaped ohmic electrode comprises an ohmic electrode strip array (3) and an ohmic electrode pad (4) connected with each other; the finger-shaped Schottky electrode comprises a Schottky electrode strip array (6) and a Schottky electrode pad (7) connected with each other; the ohmic electrode strip array (3) and the Schottky electrode strip array (6) form an out-of-plane interdigital structure.

2. The diamond / gallium oxide UV detector of claim 1, wherein, The thickness of the intrinsic single-crystal diamond epitaxial layer (2) is 100-1000 nm, the impurity concentration is less than 1 ppm, and the defect density is less than 10 6 cm -2 .

3. The diamond / gallium oxide UV detector of claim 1, wherein, The finger-shaped ohmic electrode material is one or more of W, Ti, and Al, and the thickness is 30-200 nm; the electrode strip width of the ohmic electrode strip array (3) is 5-20 μm.

4. The diamond / gallium oxide UV detector of claim 1, wherein, The thickness of the gallium oxide layer (5) is 50-220 nm, and the thickness is at least 20 nm greater than the thickness of the finger-shaped ohmic electrode.

5. The diamond / gallium oxide UV detector of claim 1, wherein, The finger-shaped Schottky electrode material is one or more of Au, Ni, and Pt, and the thickness is 20-200 nm; the electrode strip width of the Schottky electrode strip array (6) is 5-20 μm.

6. The diamond / gallium oxide UV detector of claim 1, wherein, The lateral electrode spacing between the electrode strips of the Schottky electrode strip array (6) and the electrode strips of the ohmic electrode strip array (3) is 10-30 μm.

7. A method for fabricating the diamond / gallium oxide UV detector of claim 1, wherein, The method comprises the following steps: (1) growing an intrinsic single crystal diamond epitaxial layer (2) on a single crystal diamond substrate (1) by using an MPCVD technology, and converting a hydrogen terminal on the surface into an oxygen terminal by using ultraviolet ozone treatment; (2) forming a finger-shaped ohmic electrode on the surface of the intrinsic single crystal diamond epitaxial layer (2) by using a micro-nano processing process; (3) depositing a gallium oxide layer (5) on the surface of the intrinsic single crystal diamond epitaxial layer (2) and the surface of the finger-shaped ohmic electrode by using an ALD technology; (4) preparing a finger-shaped Schottky electrode on the gallium oxide layer (5) by using a micro-nano processing process, and forming an out-of-plane interdigital structure with the finger-shaped ohmic electrode; (5) forming a photoresist mask on the gallium oxide layer (5) by using a standard photolithography process, and performing windowing on the exposed gallium oxide by using an acid solution to expose part of the ohmic electrode pad (4).

8. The method for fabricating a diamond / gallium oxide ultraviolet detector according to claim 7, characterized in that, In step (1), the growth pressure of the intrinsic diamond layer is 90-120 Torr, the methane flow rate is 1-5 sccm, the hydrogen flow rate is 400-500 sccm, the temperature is 800-900 ℃, and the epitaxial growth rate is 0.1-5 nm / min.

9. The method for fabricating a diamond / gallium oxide ultraviolet detector according to claim 7, characterized in that, In step (3), the gallium oxide deposition conditions: background pressure of 10 -2 Pa, the growth temperature was maintained at 200-350°C.

10. The method of claim 7, wherein the diamond / gallium oxide UV detector is prepared by the steps of: In step (5), the acid solution used for etching is at least one of hydrochloric acid, nitric acid, and phosphoric acid. ​

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