Infinite-Melt Vertical Liquid-Phase Epitaxy of HgCdTe from Hg Solution: from VLWIR to SWIR

Liquid-phase epitaxy (LPE) is a material growth technology used in the fabrication of mercury cadmium telluride (HgCdTe) infrared (IR) detectors, which has historically been the highest performing solution in the IR community. This paper presents the most successful LPE technology, the “infinite-melt” vertical liquid-phase epitaxy (VLPE) from Hg-rich solutions, its current state, and the evolution of this technology. The high throughput and high yield inherent in the VLPE growth process has made it possible for producing high-performance second-generation focal plane arrays to meet a variety of requirement needs. Photodiode structures with excellent performance obtained from all wavelength band regions (VLWIR, LWIR, MWIR, SWIR), including p-on-n as well as n-on-p double-layer heterojunctions (DLHJ), have been manufactured using VLPE. We determined that defects in LPE layers can arise from a variety of sources, including the substrate or debris in the melt, which are extremely problematic to eliminate, incorrect Te composition, incorrect Cd composition, poor substrate prep, and poor decant step. After defining the most significant problems, solutions were implemented. The continuous improvement of VLPE results in better uniformity, reduced noise, and competitive die size, compared to other long-wave (LW) 2nd-generation detectors. This effort concludes with a discussion of several applications of the VLPE technology demonstrated on advanced high-performance device structures.