Theoretical analysis of optical gain in uniaxial tensile strained and n⁺-doped Ge/GeSi quantum well.

The direct gap optical gain of [100] uniaxial tensile strained and n⁺-doped Ge/GeSi quantum well (QW) is calculated. The theoretical models for strained band structures near the Γ- and L-point, optical gain and free carrier absorption are provided. Simulation results show that the optical gain can be dramatically enhanced with the help of uniaxial tensile strain and n-type doping. Furthermore, to consider the competition between gain and loss and get insight into the effects of strain and doping, the net peak gain and transparency carrier density at various strain value and doping concentration are evaluated. A net peak gain up to 2061 cm^-1 for TE-polarized light is predicted at a strain value of 4%, a doping concentration of 1x10¹⁹ cm^-3and an injected carrier density of 4x10¹⁹ cm^-3.