Department of Nanoengineering, Joint School of Nanoscience and Nanoengineering, North Carolina A&T State University, Greensboro, NC 27401, United States of America.
Nanotechnology. 2023 Apr 18;34(26). doi: 10.1088/1361-6528/acc2c6.
In this work, we present a systematic design of growth experiments and subsequent characterization of self-catalyzed molecular beam epitaxially grown GaAsSb heterostructure axial p-i-n nanowires (NWs) on p-Si <111> for the ensemble photodetector (PD) application in the near-infrared region. Diverse growth methods have been explored to gain a better insight into mitigating several growth challenges by systematically studying their impact on the NW electrical and optical properties to realize a high-quality p-i-n heterostructure. The successful growth approaches are Te-dopant compensation to suppress the p-type nature of intrinsic GaAsSb segment, growth interruption for strain relaxation at the interface, decreased substrate temperature to enhance supersaturation and minimize the reservoir effect, higher bandgap compositions of the n-segment of the heterostructure relative to the intrinsic region for boosting the absorption, and the high-temperature ultra-high vacuumannealing to reduce the parasitic radial overgrowth. The efficacy of these methods is supported by enhanced photoluminescence (PL) emission, suppressed dark current in the heterostructure p-i-n NWs accompanied by increased rectification ratio, photosensitivity, and a reduced low-frequency noise level. The PD fabricated utilizing the optimized GaAsSb axial p-i-n NWs exhibited the longer wavelength cutoff at ∼1.1m with a significantly higher responsivity of ∼120 A W(@-3 V bias) and a detectivity of 1.1 × 10Jones operating at room temperature. Frequency and the bias independent capacitance in the pico-Farad (pF) range and substantially lower noise level at the reverse biased condition, show the prospects of p-i-n GaAsSb NWs PD for high-speed optoelectronic applications.
在这项工作中，我们进行了一系列的生长实验设计，并对自催化分子束外延生长的 GaAsSb 异质结构轴向 p-i-n 纳米线（NWs）进行了后续的表征，这些 NWs 生长在 p-Si <111> 衬底上，用于近红外区域的集成光电探测器（PD）应用。我们探索了多种生长方法，以便更好地了解如何通过系统地研究它们对 NW 电和光学性质的影响来减轻一些生长挑战，从而实现高质量的 p-i-n 异质结构。成功的生长方法包括使用碲掺杂剂来补偿本征 GaAsSb 段的 p 型性质、在界面处进行生长中断以实现应变弛豫、降低衬底温度以提高过饱和度并最小化储库效应、增加异质结构 n 段的能带隙组成相对于本征区以提高吸收、以及高温超高真空退火以减少寄生的径向过生长。这些方法的有效性得到了增强的光致发光（PL）发射、异质结构 p-i-n NWs 中暗电流的抑制以及整流比、光灵敏度和低频噪声水平的提高的支持。利用优化的 GaAsSb 轴向 p-i-n NWs 制造的 PD 表现出约 1.1μm 的长波长截止，在室温下具有显著提高的响应率约为 120 A W（@-3 V 偏压）和探测率为 1.1×10 Jones。在 pF 范围内的频率和偏压独立电容以及反向偏压条件下的噪声水平显著降低，表明 p-i-n GaAsSb NWs PD 有望用于高速光电应用。
