8-band k.p modelling of the quantum confined Stark effect in Ge quantum wells on Si substrates

Abstract

Recent work using compressively strained-Ge quantum wells grown on Si1−yGey virtual substrates has demonstrated efficient modulation on a silicon substrate through the quantum confined Stark effect with performance comparable to many direct band gap III-V materials. The absorption of compressively strained-Ge quantum wells is calculated by using an 8-band k.p solver within the envelope function technique. The calculated absorption spectra provide excellent agreement with experimental results, demonstrating that the absorption is dominated by the direct band gap, and allow a number of predictions of the absorption for different polarizations, quantum well widths, electric fields, and strain to be calculated. It is also shown that some of the experimental results in the literature require tensile strained substrates to produce agreement with the theoretical calculations.