Two-color quantum-well infrared photodetector with voltage tunable peaks

A two-color quantum-well infrared photodetector with voltage tunable detection peaks is demonstrated. It is based on electron transfer between two asymmetric coupled quantum wells under an applied bias. At 10 K, the peak detection wavelength is 7.5 mum for positive bias when the electrons reside in one of the wells, and switches to 8.8 mum at a large negative bias when the electrons are transferred to the other well. The electron activation behavior of dark current in this detector depends on both temperature and bias. We observed two distinctive activation energies under negative bias for two different temperature regimes and only one under positive bias. The voltage tunability of the detector and the activation energy are well explained by the calculated energy levels and oscillator strengths of intersubband transitions in the structure. (C) 2002 American Institute of Physics.