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 Ge-Si superlattice on a relaxed Si0.5Ge0.5 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 inplane energy dispersion shows that the population inversion is local-in-k-space. For an 11 ML/11 ML superlattice (15.4 Angstrom/15.4 Angstrom), interminiband lasing between HH2 and HH1 is predicted at lambda = 2.2 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(2), a gain of G(L) = 96/cm is calculated. Alternate structures with larger expected gains are considered, Quantum-parallel, quantum-cascade, and quantum-staircase lasing are examined.