HgCdTe

HgCdTe, or mercury cadmium telluride, is a ternary II-VI semiconductor with the formula Hg1−xCdxTe. By varying the cadmium content x from 0 to 1, the material's direct bandgap is tunable across the infrared, enabling absorption from near- to far-IR. It is widely used for infrared detectors because of its strong infrared response and adjustable spectral range. The crystal is typically grown on lattice-matched substrates such as CdZnTe to minimize dislocations.

HgCdTe is grown by epitaxial methods including liquid-phase epitaxy, molecular beam epitaxy, and metal-organic chemical vapor deposition. Doping controls carrier concentration, allowing n-type or p-type material for various detector geometries such as p-n junctions, Schottky diodes, and avalanche photodiodes. Devices are usually photodiodes or photoconductive detectors and require cryogenic cooling to suppress dark current and noise.

HgCdTe detectors cover a broad infrared range and are used in astronomy, defense and security, environmental monitoring, and industrial imaging. Performance depends on composition, device design, and temperature. Major challenges include maintaining compositional uniformity, managing defects from lattice mismatch, and mitigating dark current at higher operating temperatures.