NSF-BSF: Electrical mitigation of radiation-induced defects in InAs/GaSb structures for infrared sensing

The University Of Central Florida Board Of Trustees, Orlando FL

Investigators

Abstract

Infrared (IR) photodetectors have many security-related applications ranging from night-vision and large-scale fire alarm systems to IR-sensing in the hither cosmos for interceptor seekers and early missile warning systems. As a threat of terrorism is a part of every-day reality for the US and other countries, availability of efficient and radiation hard IR detector arrays will help protecting countries from terrorism, thus saving lives and assets. Damage by energetic particles degrades the sensitivity of IR photodetectors in harsh radiation environments. This project will lead to a dramatic recovery of photodetectors based on InAs/GaSb structures. This outcome will be achieved by electrical tailoring of a fundamental property of the material, the electron diffusion length, by in-situ charge injection under applied voltage. Photodetector sensitivity will recover completely and return to the original state prior to irradiation or even exceed it. The project will advance the fundamental understanding of the nature of point and extended defects in InAs/GaSb-based semiconductors and devices. The project will integrate research and education at the graduate and undergraduate levels and features an active international partner from Tel Aviv University in Israel. This project focuses on electrical mitigation of irradiation-induced defects by charge injection into infrared photodetectors based on InAs/GaSb superlattices. The ultimate aim is to produce radiation hard and efficient devices. The project hinges on the PI's previous findings that charge injection into InAs/GaSb type-II strained-layer superlattices leads to considerable changes in the material's electronic properties, particularly the carrier diffusion length. These changes result in a several fold enhancements of the photodetector quantum efficiency. It is therefore possible to improve performance of photodetectors, affected by radiation, using short pulses of solid-state forward-bias charge injection into InAs/GaSb p-i-n devices. The project will lead to a better understanding of the interaction between InAs and GaSb semiconductors and highly energetic particles, including electrons, gamma-ray photons, and protons, as well as of the nature of radiation-induced defects. Charge injection will result in enhanced minority electron diffusion length in the p-type absorption layer of a photodetector, thus increasing the quantum efficiency for the device and "healing" the adverse impact of gamma-rays, protons, electrons, and other radiation types. A unique combination of electrical and optical studies in the PI’s lab will shed light on the mechanism, which is responsible for the effect of interest. Studies of minority carrier diffusion length will be conducted using electron beam-induced current technique at various temperatures. Deep level transient spectroscopy will allow studies of radiation-induced point defects. Spectral photoresponse measurements will assess the impact of charge injection on device quantum efficiency. The ultimate goal is to correlate charge injection regimes (current; voltage; duration) and irradiation doses, thus proceeding towards control of photodetector performance and recovery from radiation damage by purely electrical means. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.