Nonradiative relaxation times in diagonal transition Si/SiGe quantum cascade structures

The possibility to achieve long hole lifetimes in diagonal radiative transition Si/SiGe quantum cascade (QC) structures was investigated. The calculations of the band structure using a six-band k·p model and hole deformation potential scattering were reported. The calculations predicted significantly increased nonradiative lifetimes for large barrier thickness, reaching about 20 ps for 35 Å Si barrier layer width. The results show that electroluminescence measurements of a series of QC structures with varied barrier width revealed comparable efficiencies and the deduced lifetimes confirmed the model calculations.