THz 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 centred at 3.4 and 4.9 THz. . Different strain-compensated heterostructures, grown on a Si substrate by ultrahigh vacuum chemical vapor deposition, have been investigated. The design employs a vertical optical transition and the observed spectral features are well described by non-equilibrium Green’s function calculations. We observe two emission peaks that are due to a non-selective injection in the upper state of the radiative transition. Comparison with similar III-V emitters is used to deduce radiative efficiencies. We will present new results from 4 quantum well Ge/SiGe emitters based on diagonal transitions in real space.