All-carbon transparent electrode diamond ultraviolet detector and preparation method thereof

Abstract

The invention discloses an all-carbon transparent electrode diamond ultraviolet detector and a preparation method thereof, and the method comprises the steps: growing an intrinsic diamond epitaxial layer and a p-type heavily-doped diamond layer on an intrinsic monocrystal diamond substrate; forming an interdigital photoresist mask with a pad on the p-type heavily doped diamond layer, and etching the unmasked p-type heavily doped diamond layer to obtain a p-type heavily doped diamond electrode array and a p-type heavily doped diamond electrode pad; removing the mask, and forming a metal electrode pad on the surface of the p-type heavily doped diamond electrode pad; and growing an unintentionally doped intrinsic diamond layer in an area outside the metal electrode pad, and oxidizing the hydrogen terminal surface into an oxygen terminal surface to obtain the detector. The problems of ultraviolet absorption and blocking of a metal electrode material of a current diamond ultraviolet detector and interface contact between other transparent electrode materials and diamond are solved, so that the responsivity of the device is improved, and the performance and the application prospect of the diamond ultraviolet detector are improved.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a fully carbon transparent electrode diamond ultraviolet detector and its preparation method. Background Technology

[0002] Ultraviolet (UV) photoelectric detection technology plays a crucial role in many key fields, such as space flame monitoring, smoke alarm systems, and space communication technology. Because the application scenarios of this technology are often extremely demanding, the performance requirements for detector materials are very stringent. Compared to silicon, a conventional semiconductor material, diamond has advantages such as a large bandgap (5.47 eV), high thermal conductivity (2200 W / mK), strong radiation resistance, and high resistivity, making it an ideal material for manufacturing UV detectors.

[0003] Traditional diamond ultraviolet detectors use metals (such as Au, Ti, and W) as electrode materials. Although metals have high conductivity and good stability, they block ultraviolet light from entering the detector, reducing the light absorption area and limiting the improvement of the detector's responsivity.

[0004] To increase the light absorption area of ​​the detector, transparent graphene has been selected as the electrode material for diamond ultraviolet detectors. However, the contact interface between graphene and diamond limits the responsivity. Therefore, it is urgent to develop a detector that optimizes the electric field distribution and photosensitive area to improve carrier concentration and collection efficiency. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a fully carbon transparent electrode diamond ultraviolet detector and its preparation method.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a fully carbon transparent electrode diamond ultraviolet detector, characterized in that: the fully carbon transparent electrode diamond ultraviolet detector comprises, from bottom to top, an intrinsic single crystal diamond substrate, an intrinsic diamond epitaxial layer, a p-type heavily doped diamond electrode array, a p-type heavily doped diamond electrode pad, a metal electrode pad, and an unintentionally doped intrinsic diamond layer.

[0009] The array of p-type heavily doped diamond electrode strips is disposed on the intrinsic diamond epitaxial layer, with alternating positive and negative polarities, and is connected to the corresponding positive and negative polarity p-type heavily doped diamond electrode pads; the metal electrode pads are disposed on the p-type heavily doped diamond electrode pads; and the unintentionally doped intrinsic diamond layer is disposed on the entire surface outside the metal electrode pads.

[0010] As a preferred embodiment of the all-carbon transparent electrode diamond ultraviolet detector of the present invention, the intrinsic single-crystal diamond layer substrate is obtained by high-temperature and high-pressure synthesis or by chemical vapor deposition; the thickness is 100-1000 μm, the surface roughness is less than 2 nm, and the defect density is less than 10. 5 cm -2 The impurity concentration is less than 1 ppm.

[0011] As a preferred embodiment of the all-carbon transparent electrode diamond ultraviolet detector of the present invention, the intrinsic diamond epitaxial layer has a thickness of 100-1000 nm, an impurity concentration of less than 10 ppb, and a defect density of less than 10. 5 cm -2 .

[0012] As a preferred embodiment of the all-carbon transparent electrode diamond ultraviolet detector of the present invention, the doping concentration of the p-type heavily doped diamond electrode array is not less than 10. 20 cm -3 The width is 1-50μm, the spacing is 5-50μm, and the thickness is 2-20nm.

[0013] As a preferred embodiment of the all-carbon transparent electrode diamond ultraviolet detector of the present invention, the metal electrode pad is a refractory metal, including metals W and Ti; the length is 100-200μm, the width is 100-200μm, the thickness is 100-500nm, and its position is far away from the p-type heavily doped diamond electrode array region.

[0014] As a preferred embodiment of the all-carbon transparent electrode diamond ultraviolet detector of the present invention, the thickness of the unintentionally doped intrinsic diamond layer is 25-50 nm, and the thickness is at least 20 nm greater than the thickness of the p-type heavily doped diamond layer.

[0015] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for fabricating a fully carbon transparent electrode diamond ultraviolet detector, comprising:

[0016] An intrinsic diamond epitaxial layer and a p-type heavily doped diamond layer were sequentially grown on an intrinsic single-crystal diamond substrate using MPCVD technology.

[0017] A photoresist mask with pads is formed on a p-type heavily doped diamond layer using standard photolithography. The unmasked p-type heavily doped diamond layer is then etched using ICP until the intrinsic diamond epitaxial layer is exposed, thus obtaining a p-type heavily doped diamond electrode array and p-type heavily doped diamond electrode pads.

[0018] Remove the mask and use micro-nano fabrication technology to form a metal electrode pad on the surface of a p-type heavily doped diamond electrode pad;

[0019] An unintentionally doped intrinsic diamond layer was grown in the region outside the metal electrode pad using MPCVD technology, and then the hydrogen-terminated surface was oxidized to an oxygen-terminated surface to obtain a detector.

[0020] The growth pressure of the intrinsic diamond epitaxial layer is 90-120 Torr, the methane flow rate is 5-20 sccm, the hydrogen flow rate is 400-500 sccm, and the temperature is 850-1000℃.

[0021] As a preferred embodiment of the preparation method described in this invention, the growth pressure of the p-type heavily doped diamond layer is 100-130 Torr, the methane flow rate is 1-6 sccm, the B2H6 flow rate is 20-50 sccm, the hydrogen flow rate is 400-500 sccm, and the temperature is 1000-1100℃.

[0022] In a preferred embodiment of the preparation method described in this invention, the etching depth is greater than the thickness of the p-type heavily doped diamond layer.

[0023] As a preferred embodiment of the preparation method described in this invention, the growth pressure of the unintentionally doped 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.

[0024] Beneficial effects of this invention:

[0025] (1) The present invention uses p-type heavily doped diamond as a transparent electrode, which can transmit deep ultraviolet light and increase the light absorption area of ​​the detector. At the same time, it can obtain good interface characteristics through homoepitaxialization, so that the device has good performance.

[0026] (2) After ICP etching, the present invention can repair etching defects by growing diamond film again, which is beneficial to improving sensitivity and response speed. Furthermore, the grown diamond film embeds p-type heavily doped diamond electrode into the material, which optimizes the electric field distribution and is beneficial to carrier collection.

[0027] (3) The present invention uses boron-doped diamond as an electrode, which has very high stability and reliability and can be used for detection in extreme environments such as high temperature and strong radiation. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0029] Figure 1 This is a three-dimensional schematic diagram of the all-carbon transparent diamond ultraviolet detector of the present invention, wherein 1 is an intrinsic single-crystal diamond substrate; 2 is an intrinsic diamond epitaxial layer; 3 is a p-type heavily doped diamond electrode array; 4 is a p-type heavily doped diamond electrode pad; 5 is a metal electrode pad; and 6 is an unintentionally doped intrinsic diamond layer.

[0030] Figure 2 This is a cross-sectional view of the all-carbon transparent diamond ultraviolet detector of the present invention, wherein 2 is the intrinsic diamond epitaxial layer; 3 is the p-type heavily doped diamond strip electrode; and 6 is the unintentionally doped intrinsic diamond layer.

[0031] Figure 3 This invention provides a performance comparison between transparent electrode diamond ultraviolet detectors and metal electrode detectors in embodiments of the present invention. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0035] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available.

[0036] Example 1

[0037] This embodiment provides a method for fabricating a fully carbon transparent electrode diamond ultraviolet detector:

[0038] (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa synthesized by high temperature and high pressure method, with a thickness of 100 μm. It was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then purged with nitrogen for 20 s. Then it was placed in an MPCVD equipment to grow a 1 μm intrinsic diamond epitaxial layer and a 2 nm p-type heavily doped diamond layer in sequence. The growth pressure of the intrinsic diamond epitaxial layer was 90 Torr, the methane flow rate was 5 sccm, the hydrogen flow rate was 480 sccm and the temperature was 900℃. The growth pressure of the p-type heavily doped diamond layer was 100 Torr, the methane flow rate was 4 sccm, the B2H6 flow rate was 25 sccm and the hydrogen flow rate was 480 sccm and the temperature was 1050℃. The doping concentration was 1×10⁻⁶. 20 cm -3 .

[0039] (2) An interdigitated photoresist mask was formed on the surface of a p-type heavily doped diamond layer using standard photolithography. The unmasked area was then etched to 4 nm using an ICP etching apparatus. After removing the photoresist mask, a p-type heavily doped diamond strip electrode array and a p-type heavily doped diamond electrode pad were obtained. The electrode strips were 1 μm wide and 1 μm apart. Then, a 100 μm × 100 μm tungsten metal electrode pad with a thickness of 100 nm was formed on the p-type heavily doped diamond electrode pad using micro-nano fabrication technology.

[0040] (3) Finally, the sample was placed in an MPCVD device to grow an unintentionally doped diamond layer. The growth pressure was 90 Torr, the methane flow rate was 1 sccm, the hydrogen flow rate was 480 sccm, the temperature was 900℃, and the thickness was 25 nm. The hydrogen terminal was oxidized to an oxygen terminal by ultraviolet ozone treatment to obtain a fully carbon transparent electrode diamond ultraviolet detector.

[0041] Example 2

[0042] This embodiment provides a method for fabricating a fully carbon transparent electrode diamond ultraviolet detector:

[0043] (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa synthesized by CVD, with a thickness of 500 μm. It was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 min, and then purged with nitrogen for 20 s. Then, it was placed in an MPCVD instrument to grow a 500 nm intrinsic diamond epitaxial layer and a 10 nm p-type heavily doped diamond layer sequentially. The growth pressure of the intrinsic diamond epitaxial layer was 90 Torr, the methane flow rate was 10 sccm, the hydrogen flow rate was 480 sccm, and the temperature was 850 °C. The growth pressure of the p-type heavily doped diamond layer was 110 Torr, the methane flow rate was 2 sccm, the B2H6 flow rate was 20 sccm, the hydrogen flow rate was 450 sccm, and the temperature was 1000 °C. The doping concentration was 2 × 10⁻⁶. 20 cm -3 .

[0044] (2) An interdigitated photoresist mask was formed on the surface of a p-type heavily doped diamond layer using standard photolithography. The unmasked area was then etched to 15 nm using an ICP etching apparatus. After removing the photoresist mask, a p-type heavily doped diamond strip electrode array and a p-type heavily doped diamond electrode pad were obtained. The electrode strips were 10 μm wide and 10 μm apart. Then, a 150 μm × 150 μm tungsten metal electrode pad with a thickness of 150 nm was formed on the p-type heavily doped diamond electrode pad using micro-nano fabrication technology.

[0045] (3) Finally, the sample was placed in an MPCVD device to grow an unintentionally doped diamond layer. The growth pressure was 90 Torr, the methane flow rate was 2 sccm, the hydrogen flow rate was 460 sccm, the temperature was 850℃, and the thickness was 30 nm. The hydrogen terminal was oxidized to an oxygen terminal by oxygen plasma treatment to obtain a fully carbon transparent electrode diamond ultraviolet detector.

[0046] Example 3

[0047] This embodiment provides a method for fabricating a fully carbon transparent electrode diamond ultraviolet detector:

[0048] (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa synthesized by CVD, with a thickness of 1000 μm. It was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 10 min, and then purged with nitrogen for 20 s. Then, it was placed in an MPCVD instrument to grow a 100 nm intrinsic diamond epitaxial layer and a 20 nm p-type heavily doped diamond layer sequentially. The growth pressure of the intrinsic diamond epitaxial layer was 90 Torr, the methane flow rate was 20 sccm, the hydrogen flow rate was 480 sccm, and the temperature was 800 °C. The growth pressure of the p-type heavily doped diamond layer was 120 Torr, the methane flow rate was 1 sccm, the B2H6 flow rate was 20 sccm, the hydrogen flow rate was 450 sccm, and the temperature was 1100 °C. The doping concentration was 3 × 10⁻⁶. 20 cm -3 .

[0049] (2) An interdigitated photoresist mask was formed on the surface of a p-type heavily doped diamond layer using standard photolithography. The unmasked area was then etched to a depth of 30 nm using an ICP etching apparatus. After removing the photoresist mask, a p-type heavily doped diamond strip electrode array and a p-type heavily doped diamond electrode pad were obtained. The electrode strips were 50 μm wide and 50 μm apart. Then, a 200 μm × 200 μm tungsten metal electrode pad with a thickness of 200 nm was formed on the p-type heavily doped diamond electrode pad using micro-nano fabrication technology.

[0050] (3) Finally, the sample was placed in an MPCVD device to grow an unintentionally doped diamond layer. The growth pressure was 100 Torr, the methane flow rate was 6 sccm, the hydrogen flow rate was 460 sccm, the temperature was 800℃, and the thickness was 50 nm. The hydrogen terminal was oxidized to an oxygen terminal by oxygen plasma treatment to obtain a fully carbon transparent electrode diamond ultraviolet detector.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that an intrinsic diamond epitaxial layer is grown on the surface of the intrinsic single-crystal diamond substrate, and then the surface is treated to be oxygen-terminated. The detector is obtained by fabricating interdigitated metal electrodes using micro-nano processing technology. There is no step (2) p-type heavily doped diamond layer growth and etching and step (3) unintentional doped diamond layer growth. This comparative example is a traditional interdigitated metal electrode diamond ultraviolet detector, which includes an intrinsic single-crystal diamond substrate, a diamond epitaxial layer and a metal electrode from bottom to top. The metal electrode is opaque and there is no buried electrode structure. The size parameters of its electrode array are the same as those of the device in Example 1.

[0053] Testing process: The sample is placed on the sample stage of the Agilent B1505A test equipment, and a voltage is introduced to the sample surface using a probe. The current signal of the device under light pulse is collected at a fixed voltage.

[0054] Figure 1 This is a three-dimensional schematic diagram of the all-carbon transparent diamond ultraviolet detector of the present invention. Figure 2 This is a cross-sectional view of the all-carbon transparent diamond ultraviolet detector of the present invention, comparing its performance with that of the detector in Example 1. Figure 3 As shown, the transparent electrode detector of Example 1 exhibits a larger photocurrent and faster response speed compared to the conventional metal electrode detector in the comparative example. The transparent electrode diamond ultraviolet detector prepared by this invention has a photocurrent of 300 nA, a rise time of 0.65 s, and a fall time of 0.095 s; the conventional metal electrode diamond ultraviolet detector has a photocurrent of 175 nA, a rise time of 0.25 s, and a fall time of 0.2 s. The results demonstrate that the transparent electrode diamond ultraviolet detector of this invention has higher sensitivity and a faster response speed.

[0055] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. An all-carbon transparent electrode diamond ultraviolet detector, characterized by: The all-carbon transparent electrode diamond ultraviolet detector comprises, from bottom to top, an intrinsic single crystal diamond substrate (1), an intrinsic diamond epitaxial layer (2), an array of p-type heavily doped diamond electrode strips (3), p-type heavily doped diamond electrode pads (4), metal electrode pads (5), and an unintentionally doped intrinsic diamond layer (6). The array of p-type heavily doped diamond electrode strips (3) is arranged on the intrinsic diamond epitaxial layer (2) and has alternating positive and negative polarities, and is connected to corresponding positive and negative polarity p-type heavily doped diamond electrode pads (4); the metal electrode pads (5) are arranged on the p-type heavily doped diamond electrode pads (4); and the unintentionally doped intrinsic diamond layer (6) is arranged on the entire surface outside the metal electrode pads (5).

2. The all-carbon transparent diamond ultraviolet detector of claim 1, wherein: The intrinsic single crystal diamond layer substrate (1) is synthesized by high temperature and high pressure or by chemical vapor deposition; the thickness is 100-1000 μm, the surface roughness is less than 2 nm, the defect density is less than 10 5 cm -2 , and the impurity concentration is less than 1 ppm.

3. The all-carbon transparent diamond ultraviolet detector of claim 1, wherein: The intrinsic diamond epitaxial layer (2) has a thickness of 100-1000 nm, an impurity concentration of less than 10 ppb, and a defect density of less than 10 5 cm -2 .

4. The all-carbon transparent diamond UV detector of claim 1, wherein: The doping concentration of the p-type heavily doped diamond electrode strip array (3) is not less than 10 20 cm -3 , the width is 1-50 μm, the interval is 5-50 μm, and the thickness is 2-20 nm.

5. The all-carbon transparent diamond ultraviolet detector of claim 1, wherein: The metal electrode pads are refractory metals including metal W and Ti, have a length of 100-200 μm, a width of 100-200 μm, and a thickness of 100-500 nm, and are located away from the array of p-type heavily doped diamond electrode strips.

6. The all-carbon transparent diamond ultraviolet detector of claim 1, wherein: The unintentionally doped intrinsic diamond layer (6) has a thickness of 25-50 nm, which is at least 20 nm greater than the thickness of the p-type heavily doped diamond layer.

7. The method of claim 1-6, wherein the method further comprises: The method comprises the following steps: An intrinsic diamond epitaxial layer (2) and a p-type heavily doped diamond layer are sequentially grown on the intrinsic single crystal diamond substrate (1) by using MPCVD technology; An interdigital structure photoresist mask with pads is formed on the p-type heavily doped diamond layer by using standard photolithography, and the p-type heavily doped diamond layer not covered by the mask is etched by ICP until the intrinsic diamond epitaxial layer is exposed, thereby obtaining the array of p-type heavily doped diamond electrode strips (3) and the p-type heavily doped diamond electrode pads (4); The mask is removed, and the metal electrode pads (5) are formed on the surface of the p-type heavily doped diamond electrode pads (4) by using micro-nano processing technology; An unintentionally doped intrinsic diamond layer (6) is grown on the region outside the metal electrode pads (5) by using MPCVD technology, and then the hydrogen-terminated surface is oxidized into an oxygen-terminated surface, thereby obtaining the detector. The growth pressure of the intrinsic diamond epitaxial layer (2) is 90-120 Torr, the methane flow rate is 5-20 sccm, the hydrogen flow rate is 400-500 sccm, and the temperature is 850-1000 °C.

8. The production method according to claim 7, characterized by: The growth pressure of the p-type heavily doped diamond layer is 100-130 Torr, the methane flow rate is 1-6 sccm, the B2H6 flow rate is 20-50 sccm, the hydrogen flow rate is 400-500 sccm, and the temperature is 1000-1100 °C.

9. The production method according to claim 7, characterized by: The etching depth is greater than the thickness of the p-type heavily doped diamond layer.

10. The production method according to claim 7, wherein: The growth pressure of the unintentionally doped intrinsic diamond layer (6) 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.

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