Multi-color infrared sensing with superlattice quantum dot structures and absorption enhancements

A multi-color superlattice quantum dot infrared photodetector consisting of two quantum dot superlattices (QD-SLs) separated by a graded barrier is reported. In each QD-SL, self-assembled QDs with a 6 nm height and a 200 nm base are embedded in a GaAs/AlGaAs superlattice. This device structure enables photocurrent generation only in one superlattice depending on the applied bias voltage polarity. A preliminary device has shown two prominent response wavelength bands with peak wavelengths at 4.9 and 7.3 ¿m at temperatures up to 120 K for negative and positive bias voltages, respectively. As an approach to enhance the light absorption efficiency, the use of metal grating induced surface plasmons is also discussed. Although, this method is not suited for QDIPs due to present growth limitations, it can be readily applied for free-carrier based heterojunction detectors.