Threshold Current Increase in GaAs/AlGaAs Quantum Cascade Lasers due to the Thickness Variation

Abstract

GaAs/AlGaAs quantum cascade laser (QCL) epi-structures were grown and lased successfully at 77 K. The thickness variation during the growth sequence was measured by analyzing the transmission electron microscope pictures. The thickness of the epi-layer decreased by up to 80 similar to 90 % of its expected value. At least three times higher threshold current and shorter lasing wavelength, compared to the reference QCL, were shown. The decrease in the growth rate during the growth sequence is thought to be a possible reason for such a high threshold current and short lasing wavelength.