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 (R-L= 11.5 K/ W), the cross-plane thermal conductivity [k perpendicular to= 2.0 +/- 0.1 W/(Km)], and the thermal boundary resistance [TBR=(4.1-9.3) x 10(-10) K/W m(2)] in strain-compensated Ga0.609In0.391As/ AlIn0.546As0.454 quantum-cascade lasers operating at 4.78 mu m in continuous wave up to 15 degrees C and in pulsed mode up to 40 degrees C. Submonolayer thick InAs and AlAs delta 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 delta layers allows for a 43% improvement of the thermal conductivity with respect to conventional lattice-matched GaInAs/ AlInAs heterostructures.