Optimization of growth conditions for InGaAs/InAlAs/InP quantum cascade lasers by metalorganic chemical vapor deposition

We investigate the growth conditions for lattice-matched InGaAs/InAlAs/InP quantum cascade lasers (QCLs) by metalorganic chemical vapor deposition (MOCVD). Effect of substrate misorientation, growth temperature, and V/III ratios of InGaAs and InAlAs layers on the surface morphology, optical quality, and impurity incorporation were systematically studied. It was found that epitaxial layers and multiquantum-well structures grown at 720 degrees C with V/Ill ratios of 116 for InGaAs and 21 for InAlAs on InP substrates with an off-cut angle of similar to 0.06 degrees exhibit a stable step-flow growth and low oxygen and carbon contamination. Using these conditions, a similar to 11.3-mu m-thick QCL with an emission wavelength at similar to 9.2 mu m was grown and fabricated, which demonstrated excellent structural quality and operated at room temperature in pulsed mode with a threshold current density of 2.0 kA/cm(2) and a slope efficiency of 550 mW/A. (C) 2010 Elsevier B.V. All rights reserved.