Thermal Characteristics of InP-based Mid-infrared Quantum Cascade Lasers at λ ∼ 8.8 μm

We have theoretically investigated the thermal characteristics of double-channel ridge-waveguide InGaAs/AlInAs quantum cascade lasers (QCLs) emitting at λ ∼ 8.8 µm in comparison with the experimental results. Based on the measured data, the thermal parameters were obtained with heat source densities using a two-dimensional anisotropic heat dissipation model. For 21 µm × 4 mm QCLs, the thermal conductance (Gth) value was 215.5W/K-cm2 at 298 K in continuous-wave (CW) operation. The Gth value was significantly increased by using a buried heterostructure (BH) via the regrowth of undoped InP layer around the laser ridge. Also, an additional improvement in the Gth was made by the use of a diamond submount, and the temperature dependency of the devices was largely decreased. The Gth value was improved to 306.7 W/K-cm2 at 298 K in the CW mode for epilayer-down bonded BH QCLs with an InP embedded layer on a diamond submount.