Accelerated Program for Low-cost CdZnTe/GaAs/Si Substrates for MCT Infrared FocalPlane Arrays

摘要

The objective of this program was to develop CdZnTe/GaAs/Si alternativesubstrates by metalorganic chemical vapor deposition (MOCVD) for MCT liquid-phase epitaxy (LPE). The purpose was to make available larger, more robust, and far less expensive substrates than currently produced bulk CdZnTe, the substrates should be compatible with LPE and free of the limitation on detector array dimensions imposed by the thermal expansion mismatch between mercury-cadmium-telluride and bump-bonded silicon circuitry. As a result at the substrate I program a thermal oxide encapsulant has been developed that is impervious to the Te-rich LPE melt and is not wetted by it. This encapsulant has made it possible to reduce the Ga impurity level in LPE HgCdTe to below 1 x 10 to the 15th atoms/cu. cm. At the same time it has been found possible to produce CdZnTe deposits with a (111) B orientation that are free of twins at the surface and are of excellent crystalline quality with dislocation densities of down to 500,000/sq cm and an X-ray rocking curve FWHM of below 80 arc sec. Long-wave infrared diodes with a quantum efficiency of 50% (when illuminated through the uncoated Si substrate) have been produced form this material. (MM).