Lateral current injection lasers: underlying mechanisms and design for improved high-power efficiency

The lateral current injection (LCI) laser-a promising technology for enabling optoelectronic integrated circuits and photonic devices with novel functionalities-is studied by comparison with conventional vertical injection devices. Fully self-consistent two-dimensional (2-D) simulations of lateral and vertical lasers reveal physical effects unique to the lateral injection class of devices. We find that (1) strong lateral carrier confinement is critical to efficient LCI laser operation, even if the active region is wide, in view of ambipolar effects, (2) current paths in parallel with the active region, even if they consist of high-bandgap intrinsic material, may nevertheless admit significant parasitic leakage even at moderate injection levels, and (3) a straightforward, but powerful, solution to the problem of premature roll-off in lasing efficiency may be achieved via heavy contact doping without significantly increasing modal free-carrier absorption.