THz intersubband electroluminescence from n-type Ge/SiGe quantum cascade structures

We report electroluminescence originating from L-valley transitions in n-type Ge/Si0.15Ge0.85 quantum cascade structures centered at 3.4 and 4.9THz with a line broadening of Delta f / f approximate to 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 a similar GaAs/AlGaAs structure yields one order of magnitude lower emission efficiency.

Automated summary

Electroluminescence from L-valley transitions in n-type Ge/Si0.15Ge0.85 quantum cascade structures has been reported, with two peaks indicating suboptimal injection in the upper state of the radiative transition. The emission efficiency of the Ge/SiGe structure is found to be one order of magnitude lower compared to a similar GaAs/AlGaAs structure.