Theory of the strain-symmetrized silicon-based Ge-Si superlattice laser

A unipolar p-i-p silicon-based intersubband laser consisting of a symmetrically strained GeSi superlattice on a relaxed Si/sub 0.5/Ge/sub 0.5/ buffer layer is modeled and analyzed. The strain-symmetrization removes the limitation on the size of the superlattice. The procedure for calculating the in-plane energy dispersion is extended to a superlattice. Analysis of the in-plane energy dispersion shows that the population inversion is local-in-k-space. For an 11 ML/11 ML superlattice (15.4 /spl Aring//15.4 /spl Aring/), interminiband lasing between HH2 and HH1 is predicted at /spl lambda/=2.2 /spl mu/m. From the envelope functions and material properties, the miniband lifetimes and laser gain are calculated. For a current density of 10 kA/cm/sup 2/, a gain of G/sub L/=96/cm is calculated. Alternate structures with larger expected gains are considered. Quantum-parallel, quantum-cascade, and quantum-staircase lasing are examined.