Characteristics of integrated QWIP-HBT-LED up-converter

In this paper, we evaluate characteristics of a novel device based on the integration of a quantum well IR photodetector (QWIP), a heterostructure bipolar transistor (HBT), and a light-emitting diode (LED) for up-conversion of middle infrared (IR) into near IR (visible) radiation. Its operation is associated with intersubband absorption of middle IR radiation in the QWIP, amplification of the QWIP output electric signal in the HBT, and emission of near IR or visible radiation from the LED fed by the current injected from the HBT. This device allows us to use Si sensors for IR and thermal imaging and significantly surpass the one based on integration of a QWIP and a LED. If the HBT current gain is high enough, the total noise of the IR camera with the up-converter can be comparable to that of the QWIP electrically connected to a read-out circuit. The major sources of the excess noise are shot noise and 1/f noise of the HBT and shot noise of the charge coupled device (CCD) sensor. The criteria to reduce their influence are established. The QWIP-HBT-LED up-converter becomes most advantageous for megapixel focal plane arrays and high read-out rate cameras.