Physical characteristics of band-gap engineered, photovoltaic detectors

A comprehensive understanding of the physics of a graded band-gap, photovoltaic detector has been achieved through a full scale finite difference simulation of the semiconductor equations and the Poisson equation in time and space. The results show that three characteristic times, Maxwell’s dielectric relaxation time, the electron transit time across a graded device period, and the minority electron lifetime, govern the transient response of the device completely. Varying device parameters to control these characteristic times will enable tailoring of device structures to optimize responsivities for applications requiring picosecond to nanosecond response speeds.