A theoretical study of resonant cavity-enhanced photodectectors with Ge and Si active regions

Abstract

An integration of Ge or Si with compound semiconductors is considered for optical detectors at wavelengths ranging from the visible to 1.55 μm. Both Ge and Si are indirect band gap materials with relatively small absorption coefficients but very long carrier lifetimes. Using a resonant cavity formed by large band gap compound semiconductor mirrors surrounding Ge and Si active layers, high photosensitivity for thin (<0.5 μm) absorbing layers can be achieved. Two different methods are discussed and compared for the calculation of the photosensitivity of resonant cavity enhanced detectors. The standing wave effect and its dependence on cavity parameters are analyzed. Design rules for such resonant cavity enhanced photodetectors are presented. The spectral response of some device designs to achieve high quantum efficiency and wavelength selectivity has also been theoretically investigated.