For strategic material development required for IRFPA technologies, bulk crystals of semiconducting materials, e.g Cadmium Zinc Telluride (CZT, Zn = ~ 4%), epitaxial layers of HgCdTe or Mercury Cadmium Telluride (MCT) and Germanium (Ge, Sb doped) are grown and fabricated into required sizes and quality in the laboratory according to DRDO's Technology Focus newsletter.

Over the years several technological achievements, breakthroughs and product development has taken place in these areas. CZT substrates are used for in-house growth of MCT epitaxial layers for the IRFPA development, a major thrust area of the laboratory. Due to strategic importance, device quality MCT epilayers and IRFPA grade CZT substrates are not available to India. Major players in HgCdTe-based IRFPA technologies worldwide do mainly rely on in-house prepared material.

Self-reliance has been achieved in both CZT and MCT, IRFPA materials required for the laboratory’s IR device development. CZT substrates are regularly produced in India with industry partner using the SSPL developed technology and MCT epitaxial layers are grown at SSPL on these supplied substrates, which are then used for device fabrication.

The laboratory indigenously developed a production worthy technology for CZT crystal growth and fabrication of substrates and established a production facility in the country for their regular production. The baseline technology has been constantly upgraded by continuous R&D efforts of SSPL for further enhancing the material quality, yield, and substrate size and simultaneously incorporated in production line. The technology has matured to a level to produce large area (30 mm x 40 mm) CZT substrates of international standards.

MCT technology has been indigenously developed and established on CZT substrates produced in the country. Demonstration of the technology has been done by fabricating detector array on them. MCT epitaxial layers for Middle Wave Infrared (MWIR) applications are grown in the laboratory using Liquid Phase Epitaxy (LPE) technique and characterized.

Device quality, fully characterised epilayers are regularly supplied and used for the detector array fabrication in the laboratory. IR thermal image has been obtained on this material thereby demonstrating the IR material technology of SSPL.

SSPL’s IR programme solely depends on the CZT substrates produced at production facility developed in India and in-house MCT epilayers grown on them.