A New Wavelength Selective FIR Detector with High Gain and Low Dark Currents

Abstract

Some time ago a new FIR detector has been demonstrated by Levine, Choi, Bethea, Walker and Malik, which used the wavelength selective intersubband absorption and subsequent emission of electrons in a multiple quantum well (MQW) structure with an electric field applied in the direction normal to the layers /1/. A major drawback of this detector is the fact, that it is a majority carrier device. The photon-assisted field emission of electrons from the individual QW's causes positive space charge in the structure. In order to avoid a time- and optical-power dependent space charge, resulting in undesirable effects similar to those of space charge limited currents, rather high dark currents are required in order to maintain macroscopic neutrality in the system.