<title>GaAs-based CCD structure for MWIR/LWIR imaging applications</title>

A new approach to sensing with intersubband absorption is introduced. In contrast to the conventional Quantum Well Infrared Photodetector (QWIP) which is a multi-quantum well device, our structure has 1 - 3 wells and uses resonant enhancement to achieve nearly complete absorption. In the QWIP the dark current is limited by the quantum well barrier in the range of 0.125 ev and thus cryogenic cooling is required in general to achieve BLIP operation. In the new structure, the dark current is limited by the band gap of GaAs/AlGaAs layers (>= 1.4 eV). This difference implies that BLIP operation may be possible near room temperature. The detecting quantum well is used to form the storage well of an active pixel or a CCD device and the intersubband absorption mechanism removes charge from the quantum well starting from the full well condition. The state of depletion of the well is then clocked to the output amplifier as in a conventional CCD using noise reduction techniques such as correlated double sampling. Therefore, the hybrid bump bonding of the Si ROIC is no longer required. In this paper, we describe the concept and its advantage vis-a-vis the existing approach and a preliminary analysis of the sensitivity of the detection.