Long wavelength infrared photocurrent study of Si-SiGe heterostructures

Abstract

We report on an experimental long wavelength infrared photocurrent study of a series of a Si-SiGe double-heterostructure samples. The active region is a thin heavily p-type doped SiGe layer, and the photoexcited holes due to free-carrier absorption are collected over the potential barrier resulting from the Si-SiGe valence-band offset. Photocurrent spectra with different cutoff wavelengths are observed for samples with different SiGe compositions, arising from internal photoemission in the Si-SiGe heterojunction. Photocurrents at finite biases and at zero bias (i.e., photovoltaic operation) are studied. Optimizing device parameters may lead to detector structures for large focal plane arrays.