p-type doped CVD diamond Schottky radiation detector and its fabrication method
By designing a multi-layer structure for a p-type doped CVD diamond Schottky radiation detector, the problems of damage and high bias voltage in existing detectors under strong radiation environments are solved, achieving low-cost, stable and efficient detection performance, suitable for harsh environments such as nuclear reactors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA INSTITUTE OF ATOMIC ENERGY
- Filing Date
- 2026-01-04
- Publication Date
- 2026-05-26
AI Technical Summary
Existing wide-bandgap semiconductor detectors are easily damaged in strong radiation environments, resulting in a surge in dark current and a decrease in detection sensitivity. Furthermore, they require an external high bias voltage, which increases the power consumption of the device and limits portable applications. Natural diamond detectors are expensive and have large purity fluctuations, making them difficult to use in large quantities.
A p-type doped CVD diamond Schottky radiation detector is adopted. It achieves bias-free operation through a p-type doped back contact layer and a Schottky barrier structure. Combined with a commercial HPHT diamond substrate and CVD epitaxy process, a multi-layer Schottky barrier structure is formed to avoid intrinsic layer impurity contamination and ensure high detection performance.
It achieves low-cost, stable and efficient detection performance, is suitable for portable devices, reduces device power consumption, has high radiation resistance and stability, is suitable for harsh environments such as nuclear reactors, and has a low performance degradation rate.
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Figure CN122094201A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ionizing radiation detection, specifically relating to a p-type doped CVD diamond Schottky radiation detector and its preparation method. Background Technology
[0002] Ionizing radiation detectors are core equipment in fields such as nuclear physics research, medical imaging diagnosis, and industrial non-destructive testing. Traditional detectors are mainly divided into three categories: gas detectors, scintillator detectors, and semiconductor detectors.
[0003] Semiconductor detectors have become a research hotspot in recent years due to their advantages such as fast response speed and high energy resolution. However, existing wide-bandgap semiconductor detectors still face significant technical bottlenecks. While natural diamond possesses excellent properties such as radiation resistance, low dark current, and chemical inertness, its "detector-grade" crystals have low yield, large purity fluctuations, and high costs, making it difficult to meet the mass application needs of industrial and medical fields. Traditional semiconductor detectors such as silicon and germanium have low radiation resistance and hardness, making them prone to lattice damage in strong radiation environments such as nuclear reactors and particle accelerators. This leads to a surge in dark current and a decrease in detection sensitivity, making long-term stable operation impossible. Some artificial diamond detectors use single-layer structures or non-optimized multilayer designs, failing to solve key problems such as "intrinsic layer impurity contamination" and "low charge collection efficiency." Moreover, most detectors require an external high bias voltage to achieve effective detection, which not only increases the power consumption and complexity of the equipment but also limits its application in portable, unpowered scenarios. Summary of the Invention
[0004] The purpose of this invention is to provide a p-type doped CVD diamond Schottky radiation detector and its fabrication method. Through the synergistic design of the p-type doped back contact layer and the Schottky barrier structure, the detector possesses the capability of operating without bias at the Schottky barrier, achieving low-cost fabrication, stable operation without bias, and high detection performance. It can be used for high-precision detection of X-rays, ultraviolet radiation, charged particles, and neutrons, and is particularly suitable for scenarios with stringent requirements for radiation resistance and stability, such as medical radiation dose measurement, accelerator beam monitoring, and nuclear reactor neutron flux monitoring.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, a p-type doped CVD diamond Schottky radiation detector, the detector comprising a metal electrode layer, an intrinsic diamond layer, a p-type doped diamond layer, and an HPHT diamond substrate, wherein the metal electrode layer, intrinsic diamond layer, p-type doped diamond layer, and HPHT diamond substrate are stacked in a layered structure from top to bottom; the metal electrode layer serves as the top electrode and forms a Schottky contact with the intrinsic diamond layer; the intrinsic diamond layer serves as the core functional region for radiation detection and is grown using a homoepitaxial CVD process.
[0006] A p-type doped diamond layer, serving as the back contact layer, is grown on the surface of an HPHT diamond substrate using an epitaxial CVD process.
[0007] Furthermore, the p-type doped diamond layer is heavily doped with boron.
[0008] Furthermore, the metal electrode layer is a circular electrode with a thickness of 100 nm and a diameter of 3 mm.
[0009] Furthermore, the metal electrode layer is made of aluminum.
[0010] Furthermore, the intrinsic diamond layer thickness is 30 μm.
[0011] Furthermore, the HPHT diamond substrate uses commercially available HPHT Ib type single crystal diamond.
[0012] Furthermore, the HPHT diamond substrate has dimensions of 4×4×0.5 mm. 3 .
[0013] Secondly, a method for fabricating a p-type doped CVD diamond Schottky radiation detector, the method being used to fabricate the p-type doped CVD diamond Schottky radiation detector described in the first aspect of the present invention and any optional embodiment thereof, the method comprising the following steps:
[0014] S1. Pre-treat the HPHT diamond substrate;
[0015] S2. The pretreated HPHT diamond substrate is subjected to homoepitaxial growth in a preset environment to generate a p-type doped diamond layer on the HPHT diamond substrate.
[0016] S3. The sample containing the p-type doped diamond layer is grown by homoepitaxial growth to form an intrinsic diamond layer on the p-type doped diamond layer.
[0017] S4. A 100 nm thick high-purity aluminum film is deposited on the surface of the intrinsic diamond layer and processed into a circular electrode with a diameter of 3 mm to form a Schottky contact. Annealed silver paste is uniformly coated on the top of the p-type doped diamond layer at a distance from the intrinsic diamond layer to form two low-resistance ohmic contacts on both sides of the intrinsic diamond layer, so as to obtain a p-type doped CVD diamond Schottky radiation detector.
[0018] Furthermore, the preset environment in step S2 includes a mixed gas of H2 and CH4 with a flow rate ratio of 100:1 SCCM, and a mixed gas of 10 SCCM of diborane-hydrogen is precisely added to the source gas. The HPHT diamond substrate temperature is stabilized at 720℃, the reaction pressure is controlled at 120 mbar, and the gas purity is CH4≥99.9995% and H2≥99.9999%.
[0019] Furthermore, before depositing a 100 nm thick high-purity aluminum film on the surface of the intrinsic diamond layer in step S4, the sample containing the intrinsic diamond layer is subjected to annealing treatment.
[0020] The beneficial technical effects of this invention are as follows: The p-type doped CVD diamond Schottky radiation detector disclosed in this invention uses a commercially available HPHT diamond substrate instead of natural diamond. Combined with mature CVD epitaxial technology, it has the advantages of high reproducibility and controllable cost, making it suitable for industrial mass production. Based on the built-in electric field of the Schottky barrier, the detector can operate stably without an external power supply, significantly reducing power consumption and structural complexity, making it particularly suitable for portable radiation detection, strong electromagnetic interference scenarios, and other environments where power supply is difficult. Diamond material itself has excellent radiation resistance and hardness. Combined with the stable back contact formed by the p-type doped layer, it can operate continuously in harsh environments with low performance degradation. The nominal intrinsic layer is grown in an independent CVD reactor, avoiding boron doping contamination at the source and ensuring a low defect concentration in the intrinsic layer. In addition, the concentration of the p-type doped layer can be precisely controlled, which helps stabilize the back contact performance and improve the batch consistency of the detector. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the structure of a p-type doped CVD diamond Schottky radiation detector shown in Embodiment 1 of the present invention. Detailed Implementation
[0022] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.
[0023] Example 1
[0024] like Figure 1 As shown, this embodiment of the invention provides a p-type doped CVD diamond Schottky radiation detector. The detector includes a metal electrode layer, an intrinsic diamond layer, a p-type doped diamond layer, and an HPHT diamond substrate arranged sequentially from top to bottom. The metal electrode layer, the intrinsic diamond layer, the p-type doped diamond layer, and the HPHT diamond substrate are stacked in a layered structure from top to bottom.
[0025] The metal electrode layer is made of high-purity aluminum (Al) material with a thickness controlled at 100nm. It is processed into a circular electrode with a diameter of 3mm, which serves as the top electrode to form a Schottky contact with the intrinsic diamond layer and is the core component of the Schottky barrier.
[0026] The intrinsic diamond layer, serving as the core functional area for radiation detection, has a thickness of 30 μm. The thickness of the intrinsic diamond layer can be flexibly adjusted according to detection requirements. It is grown using a homoepitaxial CVD process, resulting in extremely low impurity content (net active defect concentration NA = 10).14 cm -3 This ensures carrier mobility and charge collection efficiency.
[0027] A p-type doped diamond layer is used as the back contact layer, and boron is used for heavy doping, with the boron concentration precisely controlled to 10. 20 cm -3 It is grown on the surface of HPHT substrate by epitaxial CVD process. Its high conductivity can reduce back contact resistance and improve carrier transport efficiency.
[0028] The HPHT diamond substrate uses commercially available, low-cost HPHT Ib type single-crystal diamond with dimensions of 4×4×0.5 mm. 3 This provides stable support for the p-type doped diamond layer and the intrinsic diamond layer, while ensuring the mechanical strength of the overall structure.
[0029] Example 2
[0030] This invention provides a method for fabricating a p-type doped CVD diamond Schottky radiation detector. The method is used to fabricate a p-type doped CVD diamond Schottky radiation detector as described in Example 1 and any optional embodiment thereof. The method includes the following steps:
[0031] S1. Perform HPHT substrate pretreatment.
[0032] A 4mm × 4mm × 0.5mm HPHT Ib type single-crystal diamond substrate was selected. The HPHT diamond substrate was first placed in acetone and then in ethanol solutions, and ultrasonically cleaned for 15 minutes each with acetone and ethanol respectively to remove surface oil and micron-sized impurities. After cleaning, the substrate surface was dried with high-purity nitrogen and then placed in an 80℃ oven to dry, avoiding residual moisture from affecting the quality of subsequent epitaxial growth.
[0033] S2, p-type doped diamond layer growth
[0034] The pretreated substrate was transferred to the first microwave plasma-enhanced CVD reactor, and a mixture of H2 and CH4 gas (flow rate ratio 100:1 SCCM, SCCM being standard cubic centimeters per minute) was introduced. To achieve p-type doping, 10 SCCM of diborane-hydrogen mixture (containing 100 ppm B2H6) was precisely added to the source gas. Growth environment parameters were strictly controlled: substrate temperature stabilized at 720℃, reaction pressure controlled at 120 mbar, and gas purity (CH4 ≥ 99.9995%, H2 ≥ 99.9999%). Homoepitaxial growth was performed, and by controlling the growth time, a boron concentration of approximately 10 was precisely achieved. 20 cm -3The p-type doped diamond layer was grown. After growth, the reaction gas was turned off, and the sample was slowly cooled to room temperature in an H2 atmosphere to prevent thermal stress-induced delamination or defects and to avoid interlayer delamination caused by sudden temperature changes.
[0035] S3, Nominally intrinsic diamond layer growth
[0036] The sample with the p-type doped layer obtained in step S2 was transferred to a separate second microwave plasma CVD reactor to avoid contamination of the intrinsic layer by residual boron source in the first reactor. The H2 / CH4 flow ratio (100:1 SCCM), substrate temperature (720°C), and reaction pressure (120 mbar) were maintained the same as in step S2, but no doping gas was introduced. A 30 μm thick intrinsic diamond layer was formed through homoepitaxial growth to ensure low defects and high purity of the intrinsic layer, with a net active defect concentration (NA) of less than 10. 14 cm -3 .
[0037] S4. Surface Treatment and Electrode Preparation
[0038] Step S4 includes the following sub-steps:
[0039] S41. Annealing and impurity removal: Place the grown sample into an annealing furnace and anneal it at 500°C for 1 hour under argon protection to remove the H2 conductive layer remaining on the surface of the intrinsic diamond layer due to CVD growth. This can effectively reduce surface leakage current and prevent surface leakage current from affecting detection performance.
[0040] S42. Top electrode deposition: A 100nm thick high-purity aluminum (Al) film is deposited on the surface of the intrinsic diamond layer using a thermal evaporation coating process. Subsequently, it is processed into a 3mm diameter circular electrode by photolithography and etching processes to form a Schottky contact. Specifically, the pattern is defined by standard photolithography process, and the aluminum film is processed into a 3mm diameter circular top electrode using wet or dry etching technology.
[0041] S43. Back contact preparation: On the back side of the sample, i.e. on top of the p-type doped diamond layer and at a distance from the intrinsic diamond layer, annealed silver paste is uniformly coated using methods such as scraping or spin coating. Then, the sample is placed in a 150°C oven or hot plate and baked for 30 minutes to form a low-resistance ohmic contact on both sides of the intrinsic diamond layer, thus obtaining a multilayer Schottky barrier detector based on p-type doped CVD diamond.
[0042] Both low-resistance ohmic contacts are formed on top of the p-type doped diamond layer and are spaced apart from the intrinsic diamond layer.
[0043] The core working mechanism of the detector relies on the Schottky barrier formed at the interface between the metal and intrinsic diamond, combined with carrier transport optimization of the p-type doped layer. The specific process is as follows:
[0044] Schottky barrier and built-in potential: When the Al electrode comes into contact with the intrinsic diamond layer, a Schottky barrier is formed due to the difference in their work functions, which in turn generates a built-in potential. A stable internal electric field can be formed in the intrinsic layer without the need for an external bias voltage.
[0045] Radiation response and charge generation: When ionizing radiation such as X-rays and gamma rays is incident on the detector, the intrinsic diamond layer absorbs the radiation energy and generates electron-hole pairs.
[0046] Charge collection and signal output: Under the influence of the internal electric field, electrons and holes migrate to the two electrodes respectively; at the same time, charge carriers generated in the neutral region enter the depletion region through diffusion effect and are collected, effectively increasing the thickness of the sensitive layer, and finally forming a detectable current signal to realize the quantitative detection of ionizing radiation.
[0047] Key electrical and detection performance characteristics of the fabricated detector were characterized:
[0048] IV Characteristics: The current-voltage (IV) characteristics of the device were tested at room temperature using a semiconductor parameter analyzer. The results showed that the dark current of the device was less than 0.1 pA at a bias of 30 V, exhibiting an extremely low noise level.
[0049] Zero-bias operation test: Place the detector in a standard X-ray source (e.g., 137 Cs or 60 Under Co irradiation, without applying any external bias voltage, the output current was measured using a picoammeter or electrometer. The test results show that the detector can generate a stable and detectable current signal, verifying its ability to achieve passive operation by utilizing the built-in electric field of the Schottky barrier.
[0050] Preliminary radiation resistance test: The detector was placed under a certain dose of gamma-ray irradiation, and its dark current and sensitivity changes were continuously monitored. Preliminary results show that after irradiation, the device performance degradation rate is significantly lower than that of traditional silicon-based detectors under the same conditions, demonstrating the inherent high radiation resistance of diamond material.
[0051] As can be seen from the above embodiments, the p-type doped CVD diamond Schottky radiation detector and its fabrication method disclosed in this invention construct a multilayer Schottky barrier structure of "metal electrode-intrinsic diamond layer-p-type doped diamond layer-HPHT diamond substrate". The detector can work stably without an external power supply, which significantly reduces the power consumption and structural complexity of the device. The back contact conductivity is optimized by p-type doping, and the built-in potential is generated by utilizing the Schottky barrier. At the same time, the intrinsic layer is avoided from being contaminated by impurities by combining an independent CVD process.
[0052] The system and method described in this invention are not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solution of this invention also fall within the scope of technical innovation of this invention.
Claims
1. A p-type doped CVD diamond Schottky radiation detector, characterized in that: The detector comprises a metal electrode layer, an intrinsic diamond layer, a p-type doped diamond layer, and an HPHT diamond substrate. The metal electrode layer, intrinsic diamond layer, p-type doped diamond layer, and HPHT diamond substrate are stacked in a layered structure from top to bottom. The metal electrode layer serves as the top electrode and forms a Schottky contact with the intrinsic diamond layer. The intrinsic diamond layer serves as the core functional region for radiation detection and is grown using a homoepitaxial CVD process. A p-type doped diamond layer, serving as the back contact layer, is grown on the surface of an HPHT diamond substrate using an epitaxial CVD process.
2. The p-type doped CVD diamond Schottky radiation detector as described in claim 1, characterized in that: The p-type doped diamond layer is heavily doped with boron.
3. The p-type doped CVD diamond Schottky radiation detector as described in claim 2, characterized in that: The metal electrode layer is a circular electrode with a thickness of 100 nm and a diameter of 3 mm.
4. The p-type doped CVD diamond Schottky radiation detector as described in claim 1, characterized in that: The metal electrode layer is made of aluminum.
5. The p-type doped CVD diamond Schottky radiation detector as described in claim 1, characterized in that: The intrinsic diamond layer thickness is 30 μm.
6. The p-type doped CVD diamond Schottky radiation detector as described in claim 1, characterized in that: The HPHT diamond substrate uses commercially available HPHT Ib type single crystal diamond.
7. The p-type doped CVD diamond Schottky radiation detector as described in claim 6, characterized in that: The HPHT diamond substrate measures 4×4×0.5 mm. 3 .
8. A method for fabricating a p-type doped CVD diamond Schottky radiation detector, the method being used to fabricate the p-type doped CVD diamond Schottky radiation detector as described in any one of claims 1-7, the method comprising the following steps: S1. Pre-treat the HPHT diamond substrate; S2. The pretreated HPHT diamond substrate is subjected to homoepitaxial growth in a preset environment to generate a p-type doped diamond layer on the HPHT diamond substrate. S3. The sample containing the p-type doped diamond layer is grown by homoepitaxial growth to form an intrinsic diamond layer on the p-type doped diamond layer. S4. A 100 nm thick high-purity aluminum film is deposited on the surface of the intrinsic diamond layer and processed into a circular electrode with a diameter of 3 mm to form a Schottky contact. Annealed silver paste is uniformly coated on the top of the p-type doped diamond layer at a distance from the intrinsic diamond layer to form two low-resistance ohmic contacts on both sides of the intrinsic diamond layer, so as to obtain a p-type doped CVD diamond Schottky radiation detector.
9. The method for fabricating a p-type doped CVD diamond Schottky radiation detector as described in claim 8, characterized in that: The preset environment in step S2 includes a mixed gas of H2 and CH4 with a flow rate ratio of 100:1 SCCM, and a mixed gas of borane-hydrogen with a flow rate of 10 SCCM is precisely added to the source gas. The temperature of the HPHT diamond substrate is stabilized at 720℃, the reaction pressure is controlled at 120 mbar, and the gas purity is CH4≥99.9995% and H2≥99.9999%.
10. The method for fabricating a p-type doped CVD diamond Schottky radiation detector as described in claim 8, characterized in that: Before depositing a 100 nm thick high-purity aluminum film on the surface of the intrinsic diamond layer in step S4, the sample containing the intrinsic diamond layer is subjected to annealing treatment.