Electrical Properties of Oxide-Confined Vertical-Cavity Surface-Emitting Lasers

We present a comprehensive description of electrical properties of vertical-cavity surface-emitting lasers (VCSELs) based on a drift-diffusion model applied to carrie r transport in 3D multilayer semiconductor laser heterostructure with a p-n junction. We address the impact of interface grading in distributed Bragg reflectors (DBRs), modulation doping of the DBRs and surrounding layers of the quantum well (QW) as well as material-dependent carrier mobilities and recombination constants and are focused on oxide-confined GaAs/AlGaAs VCSELs. We evaluate both depletion and diffusion capacitance and show that both contributions to the capacitance as well as the differential series resistance critically depend on the injection current and chip design such that, in general, VCSEL cannot be properly modeled by an equivalent circuit approximation. Current profiles demonstrate significant inrease of the current density at the edges of the oxide-confined aperture (current crowding) which could be supressed by a proper design.