Optimum strain configurations for carrier injection in near infrared Ge lasers

The behavior of direct and indirect valleys in Ge, and the bandgap shrinking, under different tensile-strain conditions in bulk Ge and Ge quantum well structures are explored using the deformation potential and k·p methods. The doping density required for filling the indirect valleys up to the Γ-valley is calculated for various strain and growth conditions, as well as the efficiency of electron injection into the Γ-valley, and the optimum cases for Ge laser operation are identified.