组分渐变的GaAsSb纳米线生长及其高速单载流子传输特性研究

With the development of high speed laser communication, the photodetector cannot meet current requirements of miniaturization and high speed. The research of high speed nanowire photodetector is of great significance. However, slow response speed is the bottleneck that hinders the development of nanowire photodetector. So, we propose the high speed uni-traveling carriers in nanowire photodetector to solve the problem. In this project, we carry out the research of “The growth and high speed uni-traveling carrier properties of component gradient GaAsSb nanowires” from two aspects, ie. realizing uni-traveling carriers and improving the transmission performance of electrons. Through designing the energy band structure of GaAs/GaAsSb/GaSb nanowires and modifying the properties of carriers, the electrons will transfer in conduction band of GaAsSb/GaSb, the holes will relax in valence band of GaAsSb/GaAs. Then, the properties of uni-traveling carriers can be realized, which will improve the response speed of photodetector. By adjusting the band offsets properties of component gradient GaAsSb, the slope conduction band can be obtained. Under the action of built-in electric field, the transmission speed of electrons in absorb layer can be increased. Finally, the high speed uni-traveling carriers properties of GaAsSb based nanowire photodetector could be obtained. Our work laid foundation of the research of nanowire high speed photodetector.

随着激光通讯的发展，探测器已经无法满足当前对微型化和高速化的要求，因此，开展高速纳米线探测器的研究具有重要意义。目前，响应速度是阻碍纳米线探测器发展的瓶颈。针对该问题，本项目在纳米线探测器中提出高速单载流子传输的思想来提高探测器响应速度，从实现单载流子传输和提高电子传输性能两个方面开展“组分渐变的GaAsSb纳米线生长及其高速单载流子传输特性研究”的工作。通过调节GaAs/GaAsSb/GaSb纳米线能带结构，改变载流子传输特性，使电子作为单一载流子在GaAsSb/GaSb的导带传输，空穴在GaAsSb/GaAs的价带弛豫，从而实现单载流子传输，提高探测器的响应速度；通过调控组分渐变GaAsSb的带阶特性，获得倾斜的导带结构，在内建电场的作用下，提高电子在吸收层中的传输速度。最终实现GaAsSb基纳米线探测器的高速单载流子传输，为高速纳米线探测器的研究奠定基础。

本项目开展了“组分渐变的GaAsSb纳米线生长及其高速单载流子传输特性研究”的工作，从GaAsSb基纳米线的外延生长及其低维光电探测器件制备两方面来实施。采用分子束外延技术生长了高质量的GaAs纳米线、GaAs/组分渐变GaAsSb纳米线、GaAs/组分渐变GaAsSb/GaSb纳米线、GaAs/AlGaAs核壳纳米线和GaAs/GaAsSb/GaAs量子阱纳米线等结构。通过对衬底氧化层刻蚀，实现了纳米线直径、密度和垂直度的控制；并通过Sb束流控制技术，实现了组分渐变GaAsSb的可控生长。采用电子束光刻技术制备了GaAs纳米线探测器、GaAs纳米线/GaAs二维非层状片混合维度探测器和GaAs/高Sb组分GaAsSb/组分渐变GaAsSb纳米线雪崩探测器等器件;利用钝化、掺杂、少子传输通道和雪崩效应等技术，实现了GaAsSb基纳米线探测器的快速响应和高响应度特性。本项目为高性能低维光电探测器的开发提供了重要思路。