The Innovative Development of Avalanche Photodetectors for UV Application

For many miltary applications, normal photoconductors and junction photodiodes are not sufficiently sensitive for detection of low incident light levels, therefore photodetector devices with optical gain are required. Large gains can be obtained in avalanche photodiodes (APD) with both low noise and large bandwidth. It is proposed to develop innovative AlGaN/GaN based APDs. In order to achieve the objective of this proposal, two major issues have to be addressed i) the improvement of AlGaN/GaN material quality, in particular a reduction in the density of defects and ii) the development, growth, fabrication and testing of APD structures. Device structures of based on Schottky barrier and p-n junction avalanche photodetectors are proposed. The device studies will focus on investigating and measuring the avalanche breakdown voltage, the multiplication factors, the impact ionization rates, the excess noise factors and the performance of the device. In order to further decrease the noise and increase the bandwidth, a novel multi-quantum well superlattices GaN-AlxGa(1-x)N UV avalanche photodetector is proposed. The improvement GaN/AlGaN material quality and optimization of UV APD structures will result in the innovative development of a novel UV APD sensitive to low incident light levels with low noise and large bandwidth. The current interest in developing ultraviolet (UV) photodetector is driven by applications in military counter measures, aerospace, automotive, petroleum, engine monitoring, flame detection and solar W detection.