We report electroluminescence originating from L-valley transitions in n-type Ge/Si0.15Ge0.85 quantum cascade structures centered at 3.4 and 4.9 THz with a line broadening of Δf/f≈0.2. Three strain-compensated heterostructures, grown on a Si substrate by ultrahigh vacuum chemical vapor deposition, have been investigated. The design is based on a single quantum well active region employing a vertical optical transition and the observed spectral features are well described by non-equilibrium Green's function calculations. The presence of two peaks highlights a suboptimal injection in the upper state of the radiative transition. Comparison of the electroluminescence spectra with similar GaAs/AlGaAs structure yields one order of magnitude lower emission efficiency.
@article{arxiv.2101.05518,
title = {THz intersubband electroluminescence from n-type Ge/SiGe quantum cascade structures},
author = {David Stark and Muhammad Mirza and Luca Persichetti and Michele Montanari and Sergej Markmann and Mattias Beck and Thomas Grange and Stefan Birner and Michele Virgilio and Chiara Ciano and Michele Ortolani and Cedric Corley and Giovanni Capellini and Luciana Di Gaspare and Monica De Seta and Douglas J. Paul and Jérôme Faist and Giacomo Scalari},
journal= {arXiv preprint arXiv:2101.05518},
year = {2024}
}