基于InAs衬底的新型超晶格甚长波红外探测材料研究

Very long wavelength infrared (VLWIR) detectors have important and wide applications such as space based astronomy, national defense, biomedicine and environmental protection, but the great difficulty in material growth and the high dark current have seriously restricted the development of the VLWIR detection technology. We propose a new VLWIR superlattice detecting material based on the InAs substrate. Through the instead of the traditional GaSb substrate by the InAs substrate, the new material can solve the strain increasing problem and the material defect density increasing problem caused by the InAs layer thickness in one period increasing with the cutoff wavelength expanding. Through the instead of the InSb interface by the GaAs interface, the superlattice growth temperature can increase a lot, and the new approaches of reducing the material defect density and increasing the minority carrier lifetime can be further explored. Combined with the semiconductor bandengineering and a variety of measured methods, this project will explore the design and optimization of InAs-based superlattice structures and the molecular beam epitaxial (MBE) growth process of InAs-based superlattice materials, obtain the relationship between the InAs-based superlattice growth temperature, superlattice basic structure and the material properties, the response cutoff wavelength, and the minority carrier lifetime, and built the new InAs-based superlattice MBE growth technology. Based on these studies, this project will finally obtain theInAs-based superlattice material with cutoff wavelength longer than 16 μm and the corresponding single element, supplying new material technology foundation for the development of high performance VLWIR detectors.

甚长波红外探测器在航天、国防、生物医学、环保等领域有着重要而广泛的应用，但其材料制备难度大、器件暗电流高严重制约了甚长波红外探测技术的发展。本项目提出一种基于InAs衬底的新型超晶格甚长波红外探测材料，通过InAs衬底替代传统的GaSb衬底，解决随着截止波长增加InAs层厚度增加导致的应变增大、材料缺陷密度增大的问题；通过GaAs界面替代InSb界面提高超晶格生长温度，探索降低材料缺陷密度、提高少子寿命的新途径、新方法。本项目将结合半导体能带工程和多种测试手段，探索InAs基超晶格材料结构的优化设计和分子束外延生长工艺，获得InAs基超晶格甚长波探测器生长温度、基本结构与材料性能、响应截止波长、少子寿命的关系，建立新型InAs基甚长波超晶格材料的分子束外延生长工艺。在此基础上获得截止波长超过16微米的InAs基超晶格材料和单元器件，为发展高性能甚长波红外焦平面探测器提供新的材料技术基础。

甚长波红外探测器在航天、国防、生物医学、环保等领域有着重要而广泛的应用，但其材料制备难度大、器件暗电流高严重制约了甚长波红外探测技术的发展。本项目提出了一种基于InAs衬底的新型超晶格甚长波红外探测材料，并采用包络函数近似下的K.P模型，计算出了完全应变的长波InAs基超晶格的能带结构。开展了InAs基II类超晶格材料分子束外延生长研究，确定了最佳生长温度（480℃）、最优快门开关顺序和最优As平衡压（8.0×10-6 Torr），获得了系列均方根粗糙度低于0.15 nm、晶格失配低于1.0×10-5的高质量超晶格材料。开展了InAs基超晶格材料单元器件台面湿法腐蚀工艺研究，并制备了截止波长从6.5 μm到16.8 μm的多个InAs基II类超晶格单元器件；截止波长为16.8微米时，器件的暗电流密度为7.54×10-2 A/cm2，R0A为0.283 Ωcm2，峰值探测率为7.72×109 cm Hz1/2/W。开展了截止波长为10微米和12.5微米的InAs基超晶格单元器件的电学和光学性能研究，器件暗电流在75 K以上扩散电流占主导，65 K-75 K之间产生复合电流占主导，65 K以下隧穿电流占主导；与相同截止波长的GaSb基超晶格器件相比，InAs基超晶格器件的载流子寿命提高了7倍，缺陷密度降低了近一个量级；吸收区厚度为3.60微米时，截止波长为12.5微米的器件峰值响应率和量子效率分别为2.43 A/W和57.9%；量子效率谱上的震荡峰主要是由于InAs缓冲层掺杂浓度过高（2×1018 cm-3）引起的空腔效应。此外，本项目还开展了长波InAs基超晶格焦平面台面干法刻蚀工艺研究，获得了截止波长为12微米、电流响应率为1.5 A/W的320×256规模的超晶格焦平面器件。以上研究结果为发展高性能甚长波红外焦平面探测器提供了新的材料技术基础。