紫外(UV)光电探测器在空间通信、火灾探测、环境监测等领域有着广泛且重要的作用，在过去几十年受到了研究者的广泛关注。

　　GaN基pn异质结光电探测器由于具有结构简单、响应速度快以及灵敏度高等优点，特别是在没有外加电压的情况下可以实现自驱动的特性，在节约能源损耗方面表现出了巨大的发展潜力。然而，常见的天然宽带隙p型半导体(NiO、CuO等)低的空穴迁移率严重影响了GaN基pn型光电探测器的发展。因此，探究具有高空穴迁移率或高载流子浓度的宽带隙p型半导体材料并制备高效的GaN基pn型UV光电探测器具有重要意义。

　　此外，UV光电探测器的实际应用场景通常包括火灾报警和燃烧探测等高温环境，这不仅需要UV光电探测器有良好的持续运行稳定性，而且对其在恶劣环境下的运行兼容性也提出了要求。然而目前关于GaN基p-n光探测器温度依赖性的研究相对较少，因此对光探测器在不同环境温度电学特性和运行的稳定性的研究是十分必要的。

　　2023年9月10日，Applied Surface Science在线刊发了河南科技大学王辉教授课题组题为《High storage and operational stability self-powered UV photodetector based on p-CuI/n-GaN heterojunction prepared by thermal evaporation method》的研究论文。

　　该团队通过真空热蒸发法构造了一种具有自驱动功能的p-CuI/n-GaN异质结紫外光电探测器。在无偏置电压的情况下，连续运行15 h后，光电流仍能保持初始值的93.17%。此外，还研究了该光电探测器在不同环境温度(40-80℃)下的电学特性和光响应能力。随着环境温度的升高，零偏置下该探测器的光电流逐渐减小，但当器件冷却到室温时，光电流可以恢复到初始水平的95%，显示出良好的操作可逆性。更重要的是，该光电探测器具有良好的储存稳定性，在未封装和没有任何保护措施的空气中储存3个月后，光电流没有明显的退化。

　　本工作为透明和自驱动紫外光电探测器的制备提供了一种简单可行的方法，并有力地证明了p-CuI/n-GaN光电探测器在实际应用中的潜力。

Figure 1. (a) The crystal structure of CuI. (b) XRD diffraction pattern of CuI film samples, the right side is the local pattern with 2θ of 48°-58°. (c) ω-scan (swing curve) around the (111) peak. (d) Transmittance spectra of CuI film samples. (e) Absorption spectra of CuI thin film samples, inset shows band gap values. (f) PL spectra of CuI film samples. (g) Gaussian fit to the PL spectrum of sample C. (h) Temperature-dependent PL spectra of the CuI film (sample C) from 10 K to 300 K. (i) Integrated PL intensity of the CuI film as a function of reciprocal temperature.

Figure 2. (a)-(e) Scanning electron microscope (SEM) images of CuI samples (A-E), with grain size distribution statistics of the samples below and cross-sectional views of the films on the right. (f) The distribution range of grain sizes and the fitted average values for different CuI samples.

Figure 3. XPS measurements of CuI film: (a) full-scan spectra, (b) I 3d core-level spectra, and (c) Cu 2p core-level spectra. (d) The carrier concentration, resistivity and mobility of CuI samples.

Figure 4. (a) Schematic structure of the Au/p-CuI/n-GaN/In heterojunction photodetector. (b) The SEM image of cross section of p-CuI/n-GaN device. (c) I-V curves of In electrode on GaN and Au electrode on CuI. I-V characteristics of the p-CuI/n-GaN photodetector at (d) 254 nm light and (e) 365 nm light, inset show the on/off ratio of the photodetector. (f) I-V curves of the photodetector in UV light (254 nm and 365 nm) and dark. (g) Schematic diagram of band structure of p-CuI-n-GaN photodetector at ultraviolet irradiation and 0 V. (h) Responsivity spectra and (i) detectability of photodetector at zero-bias.

Figure 5. Time-dependent photo response of the p-CuI/n-GaN UV photodetector at zero bias under (a) 265 nm and (b) 365 nm light illumination. I-t response curves for (c) 254 nm and (d) 365 nm UV light at different bias voltages. (e) Estimation of the τr and τd of the photodetector at 10 Hz and 0 V. (f) Investigation of continuous operation stability of photodetectors at zero bias voltage. (g) Photodetector with 100 continuous cycles of photoresponse under 365 nm illumination.

Figure 6. (a) Dependence of p-CuI/n-GaN UV photodetector I-V characteristics on ambient temperature in darkness. (b) I-V curves of the photodetector at different ambient temperatures at 365 nm illumination. (c) I-t response curves of the photodetector at different temperatures under 0 V bias voltage. (d) I-t curves of the photodetector at RT, 80°C, and after natural cooling to RT. (e) The relationship between the on/off photocurrent ratio of the photodetector and the ambient temperature. (f) Measurement of the photodetector running at 0 V for 1 h when the ambient temperature is 80°C. (g) Photodetector photoresponse reliability measurement at 0 V after 3 months.

编辑：严志祥