MULTICOLOR INFRARED DETECTION USING A VOLTAGE TUNABLE BANDPASS FILTER

It was demonstrated that an electron energy bandpass filter placed nex t to a quantum well infrared photodetector (QWIP) is not only able to suppress dark current, but also is able to select photocurrents of dif ferent energies. Since the bandpass energy of the filter changes with an applied bias across the filter, this mechanism can be used to contr ol the detection width and the cutoff wavelength of the detector. If t he photoresponse of the QWIP has more than one energy peak, the same f ilter can also be used to intercept a particular photoelectron peak an d achieve voltage tunable multicolor infrared detection. In this work, we also show that the bandpass filter increases the background limite d temperature and the detectivity of the QWIP by filtering away the lo wer energy dark current and the unused photocurrent. (C) 1994 American Institute of Physics.