# Fileset

[NDNC2025_abstract_photodetector Gu.docx](https://mdr.nims.go.jp/filesets/bf207b70-8eed-4bee-bf2c-9cf060582782/download)

## Creator

Keyun Gu, [Zilong Zhang](https://orcid.org/0000-0002-9759-9253), Jian Huang, [Yasuo Koide](https://orcid.org/0000-0001-8321-9822), [Meiyong Liao](https://orcid.org/0000-0003-1361-4266)

## Rights

[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[Ultrahigh Gain Diamond Deep-ultraviolet Photodetector Due to Surface Hydrogen Termination and Deep defects ](https://mdr.nims.go.jp/datasets/eead8179-fc80-4c7e-8d0f-dc0652f282b1)

## Fulltext

Ultrahigh Gain Diamond Deep-ultraviolet Photodetector Due to Surface Hydrogen Termination and Deep defects Keyun Gu1,2, Zilong Zhang1, Jian Huang2, Yasuo Koide1, and Meiyong Liao1*1 National Institute for Materials Sciences, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan2 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, PR Chinameiyong.liao@nims.go.jpSolar blind deep-ultraviolet (DUV) photodetectors (PDs) are considered as a significant core of detection and communication covering civil and military due to their concealment and precision of photoelectric conversion in the 200-280 nm wavelength range [1,2]. The ultra-wide bandgap (UWBG) semiconductors such as Ga2O3, AlGaN, MgZnO, and diamond enable the development of solar-blind DUV PDs without the requirement of optical filters [3,4]. Diamond is a single-element ultra-wide bandgap (5.5 eV) semiconductor which does not have problems such as component segregation or oxygen vacancies, making it an extremely attractive material for preparing solar-blind DUV PDs [5].Up to date, a wide variety of diamond-based PDs have been developed, including Schottky diode, heterojunction, photoconductor, and metal-semiconductor-metal structure [6,7]. In spite of continuous efforts devoted to enhancing the performance of diamond DUV PDs, the sensitivity still needs to be improved and the overall performance need to be tailored based on application requirements.Herein, we demonstrate that the ultra-high quantum efficiency/gain DUV photodetectors (PDs) with low operation voltages (<5 V) can be achieved by using the synergistic effect of surface states and deep defects in a type-Ib single-crystal diamond (SCD) substrate, as shown in Figure 1. The overall photoresponse, such as the responsivity, dark current, spectral selectivity, and response speed, of the diamond DUV-PDs can be simply tailored by the surface hydrogen or oxygen termination of the diamond containing deep nitrogen defect. The DUV responsivity and external quantum efficiency (EQE) are more than 2.5x104A/W and 1.4x107%, respectively, at 220 nm-wavelength light, the highest among the DUV detectors and comparable with those of PMTs. The DUV/visible light rejection ratio (R220 nm/R400 nm) is as high as 6.7×105. The depletion of the two-dimensional hole gas on the hydrogen-terminated diamond surface by deep nitrogen defect provides a low background dark current and the filling of the ionized nitrogen upon DUV illumination induces a huge photocurrent. The synergistic effect of the surface states and the bulk deep defects opens the avenue for the development of DUV detectors with ultra-high sensitivity and low operation voltages compatible with integrated circuits.Figure 1. (a) The photodetector structure diagram. (b) Schematic energy band diagrams of PDs in dark and under illumination. Photoresponse properties vs oxidation duration. (c) Measured external quantum efficiency, EQE. (d) Responsivity, R and UV/visible rejection ratio (R220 nm/R400 nm).References1. K Gu, K. Wu……M. Liao, Adv. Funct. Mater., 2420238, (2024)2. K. Gu, Z. Zhang…… Y. Koide, M. Liao, The 19th IEEE NEMS, pp. 1-4 (2024).3. K Gu, Z. Zhang……M. Liao, L,Wang, Appl. Surf. Sci., 605: 154606 (2022).4. K Gu, Z. Zhang……M. Liao, L,Wang, J. Mater. Chem. C, 11(16): 5371-5377 (2023).5. M. Liao, Funct. Diam., 1, 29 (2019)6. M. Liao, Y. Koide, J. Alvarez, Appl. phys. lett., 90, 123507 (2007).7. M. Liao, Y. Koide, J. Alvarez, Appl. phys. lett., 87, 022105 (2005).image1.emfabc d