Intersubband Electroluminescence from GaAs/AIGaAs Triple Barrier and Quantum Cascade Structures

This paper reports: (1) the first observation of intersubband electroluminescence from a single period resonant tunnelling structure; and (2) the observation of intersubband electroluminescence from GaAs/AlGaAs-based quantum cascade structures. Intersubband emission (λ≈8.5μm) with a full width at half maximum of 7meV, was observed from a GaAs/AlGaAs triple barrier structure with quantum well widths of 66A and 33A. The emission was coupled out of the sample by a metallic grating with a period of 5μm deposited on the surface. The intensity of emission follows the resonance behaviour in the I-V character istics. In GaAs/AlGaAs quantum cascade structures, a 100A Al0.15Ga0.85As/Al0.4Ga0.6As quantum well is employed to bridge the individual active regions to enhance the overall quantum efficiency, thus greatly simplifying the design and growth of quantum cascade structures.