For several decades photomultiplier tubes (PMTs) have been the main technology for sensitive and low noise detection of photons in many high energy physics experiments. However, compared to solid-state photodetectors, PMTs are bulky, fragile, expensive, and need to be shielded from high magnetic fields and high pressures, which severely limit their application for future DOE projects. Hence, there is a need for high sensitivity photon-counting detectors that can address some of the limitations of PMTs. In the past few decades, GaN-based avalanche photodiode (APDs) have been investigated as a robust and low- cost alternative to PMTs, with some limited success. However, these APDs generally show breakdown voltages of less than 100 V, due to a large density of defect in GaN materials deposited on typical substrates, which greatly reduces their detection sensitivity, and as a results prevents their use in a number of potential scientific, industrial and defense applications. In this SBIR program, Lightwave Photonics, Inc. (LPI), in collaboration with the University of Central Florida (UCF), is proposing to develop robust GaN-based APDs by a novel technique to virtually eliminate threading dislocations in the active device layer, in order to avoid premature breakdown in these devices. We also propose to investigate multi-quantum well (MQW) AlGaN p-i-n structures that can achieve high-gain and low-noise APD operation at relatively low reverse biases of ~ 10 V. These innovations will allow the fabrication of both photon-counting detectors and large format imaging arrays that can replace PMTs in many scientific, military, and industrial applications, resulting in improved system reliability and robustness, while reducing cost, weight, size and complexity. In addition to DOE applications in high energy physics experiments, detection of light in the ultraviolet (UV) spectral range (<400 nm) has a wide range of commercial, military, and scientific applications. Some examples are UV and space-based astronomy, UV spectroscopy, gamma radiation monitoring in deep well drilling, oil spill monitoring, medical imaging, missile tracking, flame and electric arc sensing, chemical and biological hazard monitoring, and secure optical communications.
