极化增强的AlGaN日盲雪崩光电探测器研究

Solid-state avalanche photodiodes (APDs) based on AlGaN are intrinsically solar-blind, in which no additional filters are needed, and could be a viable alternative to current bulky and fragile photomultiplier tubes.AlGaN APDs have outstanding advantages such as lower operation voltages, lower power consumption, smaller sizes, and no need for cooling, which are suitable for integration into space shuttles, satellites, and some military vehicles.This project proposes a new AlGaN APD structure with polarization enhanced characteristic in order to alleviate the difficulties of the state-of-the-art growth and p-type doping of high-Al-composition AlGaN alloys.This ideal can be realized by adjusting Al composition discrepancy in different AlGaN layers and hence introducing a polarization electric field with the same direction as applied reverse-bias electric field in multiplication region of APDs.We will focus our interests on how to control synergistically lattice mismatch stress and polarization field when fabricating different AlGaN heterostructures and how to build the physical model of stress-dislocation-polarization.Meanwhile, the effects of polarization on the energy band structure and carrier impacting inonization of AlGaN device structure will be also investigated.Based on these research results, we will design and fabricate optimally the polarization enhanced AlGaN solar-blind APDs and study their performances and device physics systemically.

日盲紫外探测技术无论是在军事还是民用领域都有着极其重要的应用。本申请项目将重点针对目前发展AlGaN日盲紫外探测器存在的关键问题，挖掘材料的固有禀性，提出极化增强的雪崩光电探测器构想，以期通过利用氮化物半导体异质结构强极化特性，设计和制备出具有极化增强效应的雪崩探测器结构，缓解器件对高晶体质量的高Al组份AlGaN材料制备和p型掺杂两大难题的依赖程度，并依此深入研究基于AlGaN模板上的AlGaN异质结构外延过程中应力的调控作用，应力-位错-极化的物理关系模型，极化效应对异质界面能带带阶的调制和对载流子碰撞离化率的影响，实现雪崩光电探测器中应力和极化的综合调控，达到提高探测器雪崩增益和降低器件暗电流等目的。建立起器件性能与器件结构、材料、工艺等参数之间的关联模型，形成一套基于极化和应力调控的具有高雪崩增益的AlGaN基日盲紫外雪崩探测器设计理论。

日盲紫外探测技术无论是在军事还是民用领域都有着极其重要的应用。本项目主要开展了AlGaN日盲紫外雪崩探测器器件结构设计、极化与能带工程的调控、材料缺陷对器件性能影响以及器件可靠性等关键基础科学问题，揭示了缺陷辅助的非局域隧穿暗电流机制以及与刃位错相关的器件预击穿失效机制。首次将氮化物半导体的极化纳入紫外探测器设计中，并结合异质结能带工程，提出并制备了极化增强的AlGaN异质结日盲紫外雪崩光电探测器，其雪崩增益达到了370000，雪崩点暗电流可以控制在nA量级，国际上其他研究小组报道的增益结果集中在1000~10000，雪崩点暗电流一般在10-100nA，器件增益相比国际上其他研究小组高了一个量级。同时研制了一种具有抗反射涂层的SiN/SiO一维光子晶体结构滤波器，可有效抑制日盲波段带外光电流响应噪声，该结构在280nm-350nm波段范围内反射率超过98%，同时在短于280nm波长范围内反射低于5%。项目成果在国内外重要学术刊物上发表SCI论文23篇，授权国家发明专利2件，申请国家发明专利3件，受邀包括国际顶尖氮化物会议ICNS在内的国际/国内会议做邀请报告5次。“日盲紫外探测与应用技术”于2016年获国家技术发明二等奖和第18届中国国际工业博览会创新金奖。所研制的本征日盲型AlGaN雪崩光电探测器可应用于水质有机污染物痕量在线监测、火灾预警监测、工业发动机燃烧过程控制监测、空间紫外线剂量监测以及国防应用。