Asymmetric strain-symmetrized Ge-Si interminiband laser

We present analysis of a proposed Si-based Ge-Si superlattice p-i-p laser diode grown on a relaxed Si/sub 0.25/Ge/sub 0.75/ buffer layer. Local-in-k-space population inversion between HH2 and HH1 minibands at the superlattice minizone boundary is predicted at the 4.6-μm lasing wavelength. The 2.94-nm Ge well width is three times the 0.98-nm Si barrier width so there is no net strain. A dipole element |z/sub 21/|=5.7 /spl Aring/ is calculated, leading to an expected gain of 238 cm/sup -1/ at an injection current density of 3 kA/cm². Issues such as the waveguide design, critical thicknesses, doping levels, and expected threshold current density are addressed. Further optimization of the design is required.