Voltage-tunable two-colour quantum well infrared detector with Al-graded triangular confinement barriers

We report on a novel voltage-tunable stacked bound to quasi-continuum quant um well infrared detector designed to work in two of the atmospheric window s (3-5 and 8-12 mum) In order to improve the growth process by molecular be am epitaxy, the abrupt interfaces between different Al-content layers were eliminated. A different choice based on Al-graded triangular confinement ba rriers was used instead. This device can be voltage controlled due to the f ormation of field domains in the stacked structure when an external bias is applied. This results in a voltage drop across the detectors proportional to their series resistance. Besides, a significant photovoltaic response wa s achieved in the 3-5 mum region and attributed to an unintentional asymmet ry in the potential profile for the detector operating in this range.