Split-geometry detectors, our eyes in space

Infrared detectors have projected our ability to explore our planet and our solar system far beyond the spatial, temporal, and spectral limitations of our natural vision. As such, they are our eyes in space, constantly searching the heavens, and sending back information about the origin, constitution, and dynamics of planetary atmospheres, and other processes of interest. Their ability to do this effectively depends on their sensitivity. Today, long wave PC (photoconductive) HgCdTe detectors are the detectors of choice for applications requiring high sensitivity at long wavelengths and elevated temperature. However, planetary exploration and space surveillance of the earth's climatic condition are presently still limited by the sensitivity of available detectors. This paper will describe detectors developed at Goddard to provide enhanced performance for applications such as the CIRS/Cassini mission to Saturn and Titan, and the GOES weather satellite. Specifically, this paper will show theoretically and experimentally how detectors of split-geometry design can be exploited to increase detector resistance, responsivity, and detectivity, while decreasing 1/f noise and power dissipation. Photomicrographs of split-geometry detectors will be shown, and data demonstrating theoretical split-geometry design advantages will be presented for flight arrays built for the CIRS/Cassini mission, and for advanced detectors for GOES.