Tunable High efficiency Resonant Tunneling GaN/AlGaN MQW UV Detectors

摘要

The objective of this project is to develop tunable high efficiency resonant tunneling GaN/AlGaN multiple quantum well (MQW)-based UV photodetectors. During the grant period, more than twenty six GaN/AlGaN MQW phoptodetectors with different types of device structures and control samples have been fabricated and investigated to achieve the proposed narrow band detection, high efficiency and fast response time. The research results have been published in five refereed journals, presented at six conferences, and included in an U. S. patent application. The major accomplishments/achievements are: (a) lateral-geometry GaN/AlGaN MQW UV photodetectors were fabricated and investigated. A narrow band spectral response of 297 nm to 352 nm and a fast response speed of 50 %microns at 50 % load were achieved; (b) GaN/AlGaN heterojunction UV photodetectors were fabricated, and a high internal gain of>103 was observed. This achievement was reported as a 'Newsbreak' on page 15 in the February, 2003 issue of 'Laser Focus World'; (c) perpendicular-geometry CIaN/AIGaN MQW Schottky UV photodetectors with different barrier thickness were fabricated, and the barrier-thickness dependence of the photoresponsivity was investigated. The results show that as the barrier thickness decreases, the responsivity rapidly increases in the active wavelength range; (d) GaN/AlOaN photodetector structures using p-6H-SiC as a p-type layer in p-i-n structures as well as a substrate for the growth of AlOaN materials were fabricated and investigated to overcome two major problems: low p-type doping level in AlOaN and poor quality of AlOaN epitaxy layers on sapphire substrate; (e) in order to reduce dark current and improve photodetector performance, GaN/AlOaN p-i-n detectors were grown with a SiN dislocation-blocking layer. The extremely low dark current ( lx 10.13 A at zero bias) was observed; (f) sequential resonant tunneling in a GaN/AIGaN MQW photodetector with a SiN dislocation-blocking layer.