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In the present paper, we describe the development of Long Wave Infrared (8-12 μm) linear and 2-D IR FPA
detectors using HgCdTe for use in thermal imagers and IIR seekers. In this direction, Solid State Physics
Laboratory(SSPL) (DRDO) tried to concentrate initially in the bulk growth and characterization of HgCdTe during
the early eighties. Some efforts were then made to develop a LWIR photoconductive type MCT array in linear
configuration with the IRFPA processed on bulk MCT crystals grown in the laboratory. Non availability of quality
epilayers with the required specification followed by the denial of supply of CdTe, CdZnTe and even high purity Te
by advanced countries, forced us to shift our efforts during early nineties towards development of 60 element PC IR
detectors. High performance linear PC arrays were developed. A novel horizontal casting procedure was evolved for
growing high quality bulk material using solid state recrystallization technique. Efforts for ultra purification of Te to
7N purity with the help of a sister concern has made it possible to have this material indigenously.
Having succeded in the technology for growing single crystalline CdZnTe with (111) orientation and LPE
growth of HgCdTe epilayers on CdZnTe substrates an attempt was made to establish the fabrication of 2D short PV
arrays showing significant IR response. Thus a detailed technological knowhow for passivation, metallization, ion
implanted junction formation, etc. was generated.
Parallel work on the development of a matching CCD Mux readout in silicon by Semiconductor Complex
Limited was also completed which was tested first in stand-alone mode followed by integration with IRFPAs
through indigenously-developed indium bumps. These devices were integrated into an indigenously fabricated glass
dewar cooled by a self-developed JT minicooler. In recent years, the LPE (Liquid Phase Epitaxy) growth from Terich
route has been standardized for producing epitaxial layers with high compositional and thickness uniformity
leading to a respectable stage of maturity in FPA technology.
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