Evidence of carrier leakage into the L‐valley in InAs‐based quantum cascade lasers under high hydrostatic pressure

To investigate carrier scattering processes in short wavelength InAs/AlSb quantum cascade lasers we carried out experimental and theoretical studies of the threshold current, I th , as a function of high hydrostatic pressure and temperature. Using the calculated pressure dependence of the optical phonon scattering current, I ph , and the estimated pressure dependence of leakage current, I leak , we show that carrier leakage from the upper laser levels into the indirect L‐valley of the conduction band in InAs quantum wells is negligible in the 3.3 μm QCLs at RT leading to their superior temperature performance. In the shorter wavelength devices emitting at 2.9 μm, this loss mechanism is more important and accounts for up to 13% of I th at 190 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)