A multi-color CdS/ZnSe quantum well photodetector for mid- and long-wavelength infrared detection

In this paper, we report on the design and characterization of a quantum well based infrared photodetectors covering simultaneously infrared radiation within mid- and long-infrared spectral regions. The proposed infrared photodetectors rely on intersubband transitions in asymmetric ZnSe/CdS double quantum wells. The three-energy-level and the wavelengths of the intersubband transitions in the asymmetric double quantum wells are obtained by solving the Schrödinger and Poisson equations self consistently, the influence of the right well width on the absorption coefficient is studied. The peak positions of intersubband absorption coefficients in the structure are found at 3.31, 4.4 and 13.5 µm for a 1 nm right well width while the absorption peak positions are located at 3.33, 6.43 and 6.95 µm for a 1.4 nm right well thickness. Then, the electro-optic performances of the infrared photodetector are evaluated; the dark current dependence with the applied voltage and temperature is discussed. This work demonstrates the possibility of detection of widely separated wavelength bands using intersubband transitions in quantum wells with a low dark current.