Indium phosphide based photodiodes for mid-wave infrared detection

Mid-wave infrared (MWIR) photodetectors are used in many military and civil applications. Focal plane arrays made of these detectors are used for thermal imaging. In addition to high sensitivity, these devices require high degree of uniformity and operating temperatures close to room temperature. Current MWIR detectors are made from the mercury-cadmium-tellurium material system. These detectors suffer from poor uniformity and high fabrication costs associated with difficult device processing. MWIR detectors on Indium Phosphide substrates can take advantage of the mature materials and device technology of the Indium Phosphide material system. This material system has been used to make high performance devices for fiber optic communications for many years, and offers high uniformity and good yield. In this dissertation we present results from Indium Phosphide based p-i-n and avalanche photodiodes with cutoff wavelength of 2.4 mum. These detectors utilized lattice matched GaInAs-GaAsSb type-II quantum wells for long wavelength absorption. The p-i-n devices had low dark current at low bias, and room temperature external quantum efficiency of 43% at 2.23 mum. The avalanche photodiodes were fabricated with an InP multiplication region and showed room temperature gain above 30. At 225K, these devices showed near breakdown dark current density of 138 muA/cm 2 and gains above 200. Using strain-compensation in these type-II quantum wells, it may be possible to push the absorption of these photodiodes to longer wavelengths.