We demonstrate the influence of surface terminated V-pits in tuning dark current and spectral responsivity of Al_0.25Ga_0.75N-based UV-B photodetectors with metal–semiconductor–metal geometry on Si (111) substrate. We show that the V-pit morphological defects contribute to a large internal gain in these photodetectors, thereby leading to a substantial enhancement in external quantum efficiency (EQE) at relatively low applied biases. For photodetectors fabricated on metal organic chemical vapor deposition grown Al_0.25Ga_0.75N epilayers with a surface pit density of $2 \times 10^{8}$ cm⁻², an EQE of 100% was measured at a meager bias of 1.7 V, which increased significantly with bias. The EQE, photo-to-dark current ratio, and UV-to-visible rejection ratio measured $5 \times 10^{4}$ %, $1.2 \times 10^{4}$ , and $2 \times 10^{3}$ , respectively, at 5 V. The evidence of localized enhancement of photoresponse at the surface terminations of V-pits is exemplified by UV-assisted conductive atomic force microscopy. Temperature-dependent carrier transport analysis under dark and UV illumination revealed cumulative contributions of pit-induced thermionic field emission and hole-trapping-induced gain to the observed large EQE. This work presents the highest value of responsivity for III-nitride UV-B detectors at a given bias.

中文翻译：

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在 Si 上的 AlGaN UV-B 光电探测器中 V 凹坑诱导的光响应增强 (111)

我们证明了表面终止的 V 凹坑对调整暗电流和光谱响应率的影响，具有金属 - 半导体 - 金属几何形状的 Al _0.25 Ga _0.75 N 基 UV-B 光电探测器在 Si（111）衬底上。我们表明，V 坑形态缺陷有助于这些光电探测器的内部增益较大，从而在相对较低的施加偏压下显着提高外部量子效率 (EQE)。对于在金属有机化学气相沉积生长的 Al _0.25 Ga _0.75 N 外延层上制造的光电探测器，表面凹坑密度为 $2 \times 10^{8}$ cm ^-2，在 1.7 V 的微弱偏压下测量到 100% 的 EQE，随偏压显着增加。测量的 EQE、光暗电流比和紫外到可见光抑制比 $5 \times 10^{4}$ %, $1.2 \times 10^{4}$ ， 和 $2 \times 10^{3}$ ，分别为 5 V。紫外线辅助导电原子力显微镜举例说明了 V 凹坑表面末端光响应局部增强的证据。在黑暗和紫外线照射下的温度相关载流子传输分析揭示了凹坑诱导的热电子场发射和空穴捕获诱导的增益对观察到的大 EQE 的累积贡献。这项工作展示了 III 族氮化物 UV-B 检测器在给定偏压下的最高响应值。