Quantum cascade electroluminescence in GaAs/AlGaAs structures

The operation of a unipolar quantum cascade light-emitting diode based on the material system GaAs/AlGaAs is reported. The LED operates at a wavelength of 6.9 μm. Detailed analysis of the electroluminescence spectra shows a linewidth as narrow as 14 meV at cryogenic temperatures, increasing to 20 meV at room temperature. For typical drive-current densities of 1 kA/cm² the optical output power lies in the ten 10 nW range. Additional absorption and photocurrent measurements provide a complete characterization of the mid-infrared emitter.