Thermal analysis of buried heterostructure quantum cascade lasers for long‐wavelength infrared emission using 2D anisotropic heat‐dissipation model

Abstract

AbstractWe have theoretically investigated and compared the thermal characteristics of γ ∼ 10.6 μm InGaAs/InAlAs/InP buried heterostructure (BH) quantum cascade lasers (QCLs) with different heat‐sinking configurations by a steady‐state heat‐transfer analysis. The heat‐source densities were obtained from laser threshold power densities measured experimentally under room‐temperature continuous‐wave mode. The two‐dimensional anisotropic heat‐dissipation model was used to calculate the temperature distribution, heat flux, and thermal conductance (Gth) inside the device. For good thermal characteristics, the QCLs in the long‐wavelength infrared region require the relatively narrow BH structure in combination with epilayer‐down bonding due to thick active core/cladding layers and high insulator losses. The single‐ridge BH structure results in slightly higher thermal conductance by ∼2–4% than the double‐channel (DC) ridge BH structure. For W = 12 μm with 5 μm thick electroplated Au, the single‐ridge BH laser with epilayer‐down bonding exhibited the highest Gth value of 201.9 W/K cm2, i.e. increased by nearly 36% with respect to the epilayer‐up bonded DC ridge waveguide laser. This value is improved by ∼50% and ∼62% with respect to the single‐ridge BH laser and DC ridge waveguide laser with W = 20 μm in the epilayer‐up bonding scheme, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)