Mode and recombination control in semiconductor lasers

A self consistent mathematical description of a semiconductor GaAlAs heterostructure laser has been developed. It includes excess hole and electron injection, diffusion, drift and recombination. The excess carrier motion is described by the ambipolar diffusion equation. The boundary conditions at each heterojunction are found by imposing electron and hole current continuity as well as quasi-Fermi level continuity. The Fermi-level continuity condition is applied using Kane's non-parabolicity for the GAMMA1/sub C/ minimum and a parabolic expression for both the GAMMA15 /sub v/ and the X1/sub C/ minima. The effect of aluminum concentration on carrier mobility, effective mass and gap is included. The volume recombination rate is related to the optical gain of the laser in linear fashion using coefficients obtained by integrating over parabolic bands without quasi-momentum conservation. The recombination lifetime is found in a similar manner. The diffusion coefficients are calculated using the generalized Einstein equation. The dependence of the index of refraction in the device upon carrier injection is included. The E-M field is calculated by solving Maxwell's equations for a general five layer dielectric waveguide. Above threshold the gain is assumed to be pinned at the threshold value. For each solution, the E--M field distribution is determined self-consistently for a particular excess carrier distribution. The theory has been applied extensively to many contemporary laser structures, including double heterostructure, single heterostructure and symmetrical optical cavities. Design curves including injection efficiencies, peak power at catastrophic degradation, threshold current density and I--V characteristics have been developed for various cavity geometries and dopants