Ghosh Soumava, Sun Greg, Morgan Timothy A, Forcherio Gregory T, Cheng Hung-Hsiang, Chang Guo-En
Department of Mechanical Engineering, and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chiayi 621301, Taiwan.
Department of Engineering, University of Massachusetts-Boston, Boston, MA 02125, USA.
Sensors (Basel). 2023 Aug 30;23(17):7531. doi: 10.3390/s23177531.
Group IV alloys of GeSn have been extensively investigated as a competing material alternative in shortwave-to-mid-infrared photodetectors (PDs). The relatively large defect densities present in GeSn alloys are the major challenge in developing practical devices, owing to the low-temperature growth and lattice mismatch with Si or Ge substrates. In this paper, we comprehensively analyze the impact of defects on the performance of GeSn homojunction PDs. We first present our theoretical models to calculate various contributing components of the dark current, including minority carrier diffusion in - and -regions, carrier generation-recombination in the active intrinsic region, and the tunneling effect. We then analyze the effect of defect density in the GeSn active region on carrier mobilities, scattering times, and the dark current. A higher defect density increases the dark current, resulting in a reduction in the detectivity of GeSn PDs. In addition, at low Sn concentrations, defect-related dark current density is dominant, while the generation dark current becomes dominant at a higher Sn content. These results point to the importance of minimizing defect densities in the GeSn material growth and device processing, particularly for higher Sn compositions necessary to expand the cutoff wavelength to mid- and long-wave infrared regime. Moreover, a comparative study indicates that further improvement of the material quality and optimization of device structure reduces the dark current and thereby increases the detectivity. This study provides more realistic expectations and guidelines for evaluating GeSn PDs as a competitor to the III-V- and II-VI-based infrared PDs currently on the commercial market.
作为短波至中红外光电探测器（PD）中一种具有竞争力的材料替代品，GeSn Ⅳ族合金已得到广泛研究。由于低温生长以及与 Si 或 Ge 衬底的晶格失配，GeSn 合金中存在相对较高的缺陷密度，这是开发实用器件的主要挑战。在本文中，我们全面分析了缺陷对 GeSn 同质结 PD 性能的影响。我们首先提出理论模型来计算暗电流的各种贡献成分，包括少数载流子在 n 型和 p 型区域的扩散、有源本征区域中的载流子产生 - 复合以及隧穿效应。然后我们分析了 GeSn 有源区域中缺陷密度对载流子迁移率、散射时间和暗电流的影响。较高的缺陷密度会增加暗电流，导致 GeSn PD 的探测率降低。此外，在低 Sn 浓度下，与缺陷相关的暗电流密度占主导，而在较高 Sn 含量时，产生暗电流占主导。这些结果表明在 GeSn 材料生长和器件加工中最小化缺陷密度的重要性，特别是对于将截止波长扩展到中波和长波红外波段所需的较高 Sn 成分。此外，一项对比研究表明，进一步提高材料质量和优化器件结构可降低暗电流，从而提高探测率。本研究为评估 GeSn PD 作为目前商业市场上基于Ⅲ - V 族和Ⅱ - Ⅵ族的红外 PD 的竞争对手提供了更现实的期望和指导方针。
