The role of quantum-well states and carrier scattering times in discontinuities of opto-electrical characteristics of SCH lasers

Abstract

Drift-diffusion computer simulations model available in Synopsys’ Sentaurus TCAD is used to study electrical, I-V, and optical, I-L, characteristics of separate-confinement heterostructure laser based on AlGaAs. We investigate the role of the width and depth of Quantum Well (QW) active region, below and above the lasing threshold. The device properties depend on both, the number of bound QW states and on closeness of the highest bound states to conduction or valence band offset. The lasing action may not exist at certain widths or hights of QW, and the threshold current is a discontinuous function of these parameters. The effects are more pronounced at low temperatures. Discontinuities in characteristics are found, at certain conditions, in temperature dependencies as well. The carriers scattering time on QW is shown to have the crucial role on amplitude of discontinuities.