Image Smearing in a Quantum Well Infrared Photodetector Monolithically Integrated With a Light Emitting Diode

摘要

The recent advances in infrared sensing technology has made it possible to use infrared sensors to support environmental observations, surveillance, threat detection, tracking, and target identification. For ballistic missile defence (BMD) related applications, the most important detector requirements are: high sensitivity, high uniformity, large format, and multicolor capabilities. Quantum well infrared photodetector (QWIP) is a relatively new candidate technology for BMD applications. It has become one of the most promising near-term infrared technologies to meet mid-course detection requirements because of its wavelength flexibility in mid-infrared, far- infrared, and very far-infrared regions, as well as multicolor capabilities. Canadian QWIP technology is based on monolithic integration of quantum well infrared photodetector with a light emitting diode (QWIP-LED), and was pioneered by Dr. H.C. Liu of Institute for Microstructural Sciences, National Research Council of Canada. The goal of the present program is to realize a 1x1 sq cm(exp 2) two-color QWIP-LED imaging device by March 2001 and, eventually, to develop a very large format (up to 4x4 sq cm(exp 2)) prototype imaging camera. The success of the QWIP-LED depends critically on the extent of spatial lateral spreading of both photocurrent generated in the QWIP and near infrared photons emitted by the LED as they escape from the QWIP-LED layers. According to a LED model proposed by Schnitzer et al., there appears to be a trade-off between a high LED external quantum efficiency and a small photon lateral spread, the former being a necessary condition for achieving high detector sensitivity. The model predicts that as much as 25 reincarnations of the originally emitted NIR photons (as they spread laterally within the QWIP-LED) are required for most of the LED emitted light to escape.