EVALUATING THE EFFECTS OF OPTICAL AND CARRIER LOSSES IN ETCHED-POST VERTICAL-CAVITY LASERS

We demonstrate the combined effects of optical scattering loss and sur face recombination (or carrier diffusion) on the performance and scala bility of etched-post vertical cavity lasers (VCLs). The size dependen ce of optical losses and threshold gain are determined from pulsed mea surements of external quantum efficiency. Deeper etch depths result in a stronger radial dependence of the threshold gain, which quickly inc reases the threshold current density. With optical loss accounted for, pulsed threshold current density measurements give the extra informat ion needed for evaluating carrier loss. Surface recombination or carri er diffusion also results in threshold; current density increases, but scalability is ultimately limited by the ability of the active region to provide enough gain for smaller size, higher optical loss devices. Even with these losses, thr ee-quantum-well VCLs with shallow etches have threshold currents as low as 420 mu A. (C) 1995 American Institut e of Physics.