Avalanche photodetectors (APDs) are key components in optical communication systems due to their increased photocurrent gain and short response time as compared to conventional photodetectors. A detector design where the multiplication region is implemented in a large band gap material is desired to avoid detrimental Zener tunneling leakage currents, a concern otherwise in smaller band gap materials required for absorption at 1.3/1.55 μm. Self-assembled III–V semiconductor nanowires offer key advantages such as enhanced absorption due to optical resonance effects, strain-relaxed heterostructures, and compatibility with mainstream silicon technology. Here, we present electrical and optical characteristics of single InP and InP/InAsP nanowire APD structures. Temperature-dependent breakdown characteristics of p⁺-n-n⁺ InP nanowire devices were investigated first. A clear trap-induced shift in breakdown voltage was inferred from I–V measurements. An improved contact formation to the p⁺-InP segment was observed upon annealing, and its effect on breakdown characteristics was investigated. The band gap in the absorption region was subsequently varied from pure InP to InAsP to realize spatially separate absorption and multiplication APDs in heterostructure nanowires. In contrast to the homojunction APDs, no trap-induced shifts were observed for the heterostructure APDs. A gain of 12 was demonstrated for selective optical excitation of the InAsP segment. Additional electron-beam-induced current measurements were carried out to investigate the effect of local excitation along the nanowire on the I–V characteristics. Simulated band profiles and electric field distributions support our interpretation of the experiments. Our results provide important insight for optimization of avalanche photodetector devices based on III–V nanowires.

中文翻译：

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基于InP / InAsP纳米线的空间独立吸收和倍增雪崩光电探测器

雪崩光电探测器（APD）是光通信系统中的关键组件，因为与常规光电探测器相比，雪崩光电探测器具有更高的光电流增益和更短的响应时间。需要一种在较大的带隙材料中实现倍增区域的检测器设计，以避免有害的齐纳隧穿泄漏电流，否则对于在1.3 / 1.55μm吸收所需的较小的带隙材料来说是一个问题。自组装的III–V半导体纳米线具有关键优势，例如由于光学共振效应而增强的吸收，应变松弛的异质结构以及与主流硅技术的兼容性。在这里，我们介绍了单个InP和InP / InAsP纳米线APD结构的电学和光学特性。p ^+的温度相关击穿特性首先研究了-nn ⁺ InP纳米线器件。在击穿电压的明确陷阱引起的偏移从推断我- V测量。改善了与p ^+的接触形成退火后观察到-InP链段，并研究了其对击穿特性的影响。吸收区中的带隙随后从纯InP变为InAsP，以实现异质结构纳米线中空间分离的吸收和倍增APD。与同质结APD相反，对于异质结构APD，未观察到陷阱引起的位移。对于InAsP段的选择性光激发，增益为12。附加电子束感生电流的测量进行了调查局部激发的上沿所述纳米线的影响我- V特征。模拟的频带分布和电场分布支持我们对实验的解释。我们的结果为优化基于III–V纳米线的雪崩光电探测器提供了重要的见识。