SPONTANEOUS RECOMBINATION CURRENT IN INGAAS GAAS QUANTUM-WELL LASERS

We have studied the intrinsic factors which determine the threshold current and its temperature dependence in 160-Å-wide In0.2Ga 0.8As single well quantum lasers with GaAs barriers, grown by molecular beam epitaxy on GaAs substrates. By measuring the relative temperature dependence of the spontaneous emission intensity at threshold we show that radiative transitions between higher order (n=2,3) electron and heavy hole subbands make a significant contribution to the threshold current and its temperature sensitivity, even in devices where the laser transitions are between n=1 subbands. These higher transitions will also influence the dependence of threshold current and its temperature sensitivity on well width.