A novel Si-based LWIR detector: the SiGe/Si heterojunction internal photoemission detector

A novel Si-based long-wavelength infrared (LWIR) detector, the SiGe/Si heterojunction internal photoemission (HIP) detector, has been demonstrated. The detection mechanism of the SiGe/Si HIP detector is infrared absorption in the degenerately doped p/sup +/-SiGe layer followed by internal photoemission of photoexcited holes over the heterojunction barrier. The p/sup +/-SiGe layers are grown by molecular beam epitaxy with boron concentrations up to 4*10/sup 20/ cm/sup -3/. The cutoff wavelength of this device can be tailored by varying the valence band offset between the SiGe alloy and Si, and thus can be extended into the long-wave infrared regime. The valence based offset can be adjusted by varying the Ge ratio in the SiGe layers. Results have been obtained from test devices with Ge composition ranging from 0.2 to 0.4, giving quantum efficiencies of 3-5% for a single pass in the 8-12 mu m region.<>