Gain and internal losses in InGaAsSb InAsSbP double-heterostructure lasers

We report on a study characterizing internal losses and the gain in InGaAsS b/InAsSbP diode-heterostructure lasers emitting in the mid-infrared (3-4 mu m). Numerical simulations of the current dependence of the intensity of sp ontaneous emission above the laser threshold and of the differential quantu m efficiency allowed us to determine the intraband absorption k(0)approxima te to 5.6x10(-16) cm(2). The cavity-length dependence of the threshold curr ent is used to estimate the internal losses at zero injection current alpha (0)approximate to 5 cm(-1). Calculations of the internal losses at laser th reshold showed that they increase more than fourfold when the cavity length is decreased from 500 mu m to 100 mu m. The temperature dependence of the differential quantum efficiency is explained on the assumption that intraba nd absorption with hole transitions into a split-off band occurs. It is sho wn that the maximum operating temperature of "short-cavity" lasers is deter mined by the intraband absorption rather than by Auger recombination. The i nternal losses are shown to have a linear current dependence. The separatio n of the quasi-Fermi levels as a function of current demonstrates an absenc e of voltage saturation of the p-n junction above threshold. (C) 1999 Ameri can Institute of Physics. [S1063-7826(99)02806-9].