SBIR-STTR Award

High quality wafer of Mercury Cadmium Telluride are critically needed for the fabrication of Infrared Focal Plane Arrays. Defense related applications of these arrays include: surveillance, target detection, acquisition and tracking, missile guidance, thermal imaging, navigational aids and night vision. For operation in the back-side illuminated mode it is required that the active device layer of Mercury Cadmium Telluride be deposited on a suitable substrate material. The substrate material must meet a number of stringent requirements and the development of suitable substrate has been a formidable task. Recently Xacton has achieved a major breakthrough in the Mercury Telluride technology. Based on this, we proposed the use of high quality wafers of Mercury Cadmium Telluride as a substrate material for the epitaxial growth of active layers of Mercury Cadmium Telluride. The substrate can be made transparent to the incoming radiation by tailoring its composition to be slightly more Cd rich than that of the active epitaxial layer.

Xacton has grown single crystal wafers with a very high level of crystalline perfection, and very low level of defect density. They are extremely uniform in composition, cut off wavelength, and other properties. Any non-uniformity's observed are well within the margin of error of the measurement techniques. Based on literature data, it appears that the wafers produced by Xacton may be the only wafers that are single crystal at a microscopic level. In Phase II, Xacton will utilize these wafers for the development of high quality detector arrays and extend the process to the growth of even larger diameter wafers, namely 3" diameter. Due to the exceptionally high quality of this material, it is possible to build monolithic arrays, where both the detectors and readout electronics are built in HgCdTe. This eliminates the necessity of bump-bonding the MCT detector array to a silicon multiplexer via in-bumps. This could eliminate problems with precision bump-bonding and performance degradation during heat cycles because of dissimilar thermal properties of the MCT, the Si and the In.