Work

Damage-free lift-off of epitaxial HgCdTe thin films for future curved infrared imaging array applications

Year: 2025

Type: article

Abstract: This paper presents a study on the molecular beam epitaxial (MBE) growth of H g 0.72 C d 0.28 T e thin film materials on C d 0.96 Z n 0.04 T e (2 1 1)B substrates, incorporating a 10 nm thick MgTe sacrificial layer for subsequent lift-off. The H g 0.72 C d 0.28 T e thin films present a full width at half maximum of 31 arc sec for the X-ray diffraction rocking curve and a root-mean-square surface roughness of 1.2 nm. Additionally, this study developed and characterised an epitaxial lift-off process for the HgCdTe epilayers. The HgCdTe epilayers were successfully lifted-off from the substrate by adhering them to a silicon substrate and immersing in deionized water to dissolve the MgTe sacrificial layer. After lift-off, the samples exhibited p-type conduction with a carrier concentration of 2.01 × 10 15 c m - 3 and a hall mobility of 1.96 × 10 2 c m 2 / V · s at 77 K. Following the epitaxial lift-off process, photoconductors were fabricated on the HgCdTe thin films, which demonstrated a peak responsivity of 1080 V / W and a peak detectivity of 3.3 × 10 10 Jones at 77 K at the wavelength of 5.4 µm. The minority carrier lifetime was measured to be around 1.15 µs at 77 K. A scanned imaging system was constructed to assess the infrared imaging performance of the photoconductor. These results were then compared with those of a photoconductor fabricated on HgCdTe thin films without the epitaxial lift-off process, and indicated that the lift-off process has minimal impact on the optoelectronic properties of the thin film and on device performance. These findings validate the feasibility of producing high quality, free-standing HgCdTe thin films for future applications in curved imaging arrays.

Source: Infrared Physics & Technology

DOI: 10.1016/j.infrared.2025.106073