Analytical Modeling of the Spectral Response of Heterojunction Phototransistors

Spectral response model for heterojunction phototransistors (HPTs) is developed from resolution of continuity equations that govern the excess optically generated minority-carrier variation in the active layers of the HPT taking into account the related physical parameters. Realistic boundary conditions have been considered for efficient device operation, and a detailed optical-power absorption profile is constructed for accurate device modeling. The analysis is performed for GaAs-based HPTs, and the measured results at 635, 780, and 850 nm show a good agreement with theoretical calculations.