Band-structure dependence of impact ionization: bulk semiconductors, strained Ge/Si alloys, and multiple-quantum-well avalanche photodetectors

Abstract

The band-structure dependence of impact ionisation in bulk semiconductors strained Ge/Si alloys and multiple quantum well avalanche photodiodes was studied theoretically and experimentally. Hydrostatic pressure was used to investigate impact ionisation in Si Ge and GaAs. The results are interpreted with the aid of theoretically calculated threshold energies for impact ionisation. Calculated thresholds in strained Ge/Si alloys suggest that this material system may be of interest for low-noise photodetectors. However Monte Carlo studies of impact ionisation in multiple quantum well (MQW) avalanche photodiodes (APDs) show that the F valley conduction band offset does not lead to improved performance in GaAs/AlGaAs MQW APDs.