A New 10 μm Infrared Detector Using Intersubband Absorption in Resonant Tunneling GaAlAs Superlattices

The fabrication of 10 μ m infrared detectors from III-V materials would allow advantageous use of their highly developed growth and processing technologies, as compared with II-VI compounds. 1-2 Furthermore, device parameters (e.g. bandgap, operating temperature, bandwidth and speed) can be tailored in ways that are difficult to do with either II-VI’s or extrinsic Si detectors. We report here the first demonstration of a novel high speed infrared detector based on intersubband absorption and sequential resonant tunneling in doped GaAs/Al x Ga 1- x As quantum well superlattices. We achieved a responsivity of 0.52 A/W at λ = 10.8 μ m, an advantageous narrow bandwidth response Δλ/λ ≃ 10%, and estimate the speed to be ≈ 45 psec. From our experiments we have determined that the mean free path of the photogenerated hot electrons through the superlattice is 2500 Å.