HIGH-POWER INTER-MINIBAND LASING IN INTRINSIC SUPERLATTICES

We report the realization of a mid-infrared (lambda similar or equal t o 7 mu m) quantum-cascade laser. in which the emission process takes p lace between the two lowest minibands of an intrinsic superlattice. Co ntrary to previous lasers based on doped superlattices, here the dopan ts are located only inside suitably designed injector regions, where p ositive ionized donors and negative electrons are arranged to compensa te the applied external field across the superlattices. This reduces i mpurity scattering and translates into low threshold currents (4.2 kA/ cm(2) at 10 K) and into room temperature operation, without compromisi ng the large current-carrying capabilities of the minibands. Peak powe rs of similar to 1.3 W per facet have been obtained from broad-area de vices at 10 K, with still more than 1 W at 120 K and 400 mW at 200 K. Effects related to the finite size of the superlattices become visible in the spectral properties, owing to the reduced broadening, and have to be taken into account to accurately describe the laser's behavior. [S0003-6951(98)04419-2].