MgCdTe buffer layers for MBE growth of high-quality HgCdTe: An approach toward curved imaging arrays

For next-generation infrared imaging systems, there is a growing demand for large field of view operation with reduced optical aberrations, which has motivated the development of curved HgCdTe focal plane arrays. The realization of such curved detectors requires damage-free substrate removal while preserving high material and device quality, posing significant challenges to conventional fabrication approaches. This work presents a preliminary study on the feasibility of incorporating a MgCdTe buffer layer for the molecular beam epitaxy growth of mid-wave infrared HgCdTe on CdZnTe (211)B substrates. The impact of the MgCdTe buffer on the structural and optoelectronic properties of the overlying HgCdTe layer is systematically investigated. The HgCdTe layers exhibit high crystal quality with an x-ray rocking curve full width at half maximum of 43 arc sec and a root mean square surface roughness of 1.02 nm. Fabricated HgCdTe photoconductors show a peak responsivity of 760 V/W and a peak detectivity of 2.5 × 10¹⁰ Jones at 77 K at a wavelength of 5.4 μm, comparable to previously reported p-type HgCdTe devices. The results indicate that the incorporation of a MgCdTe buffer layer does not degrade the material or device quality of HgCdTe. Therefore, this buffer-layer platform provides a viable foundation for integration with thick MgTe sacrificial layers to enable epitaxial liftoff for curved HgCdTe detector fabrication.