Analysis of InGaAsSb/AIGaAsSb Photodetectors for Applications at the 2.0 Micron Wavelengths

The study of an InGaAsSb-based heterojunction avalanche photo detector has been carried out for 2-μm applications. A separate absorption and multiplication structure was used because it minimizes the tunneling component of the dark current in the absorption region, and also provides single-carrier injection into the multiplication region. This is a well-known requirement for reducing the multiplication noise. The primary goal was to evaluate the potential of InGaAsSb-AlGaAsSb photo-detectors for photodetection at the two-micron wavelength. InGaAsSb is a relatively new material, and, therefore, characterization and photodetector response analysis based on this material are not available in the literature. In this thesis research, studies of InGaAsSb-based heterojunction photodetectors for applications around the 2-μm wavelength have been carried out. A numerical model has been developed, and simulation results were compared to the experimental characteristics of a prototype detector with the same material composition and structure available at NASA LaRC. The predictions seem to be in good agreement with measurements. Theoretical analysis reveals the conditions for successful avalanche gain and device responsively. A sharp cut-off around 2.2-μm has been demonstrated, and values for the wavelength dependent absorption coefficient for InGaAsSb extracted. A dependence of responsivity on the bias voltage was also demonstrated. An alternate photo-detector structure has been proposed for improved performance, especially for hole transport.