Investigations of carrier scattering into L‐valley in λ = 3.5 µm InGaAs/AlAs(Sb) quantum cascade lasers using high hydrostatic pressure

In order to identify the performance limitations of InGaAs/AlAs(Sb) quantum cascade lasers, experimental investigations of the temperature and pressure dependencies of the threshold current (I-th) were undertaken. Using the theoretical optical phonon current (I-ph) and carrier leakage (I-leak) to fit the measured threshold current at various pressures, we show that the electron scattering from the top lasing level to the upper L-minima gives rise to the increase in I-th with pressure and temperature. It was found that this carrier leakage path accounts for approximately 3% of I-th at RT and is negligible at 100 K. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim