Influence of InAs, AlAs δ layers on the optical, electronic, and thermal characteristics of strain-compensated GaInAs∕AlInAs quantum-cascade lasers

We extracted the electronic temperatures, the thermal resistance (RL=11.5K∕W), the cross-plane thermal conductivity [k⊥=2.0±0.1W∕(Km)], and the thermal boundary resistance [TBR=(5–11)×10−10K∕Wm2] in strain-compensated Ga0.609In0.391As∕AlIn0.546As0.454 quantum-cascade lasers operating at 4.78μm in continuous wave up to 15°C and in pulsed mode up to 40°C. Submonolayer thick InAs and AlAs δ layers are included in the active region to increase the conduction band discontinuity. We found that potential interface broadening caused by the insertion of these δ layers allows for a 60% improvement of the thermal conductivity with respect to conventional lattice-matched GaInAs∕AlInAs heterostructures.