This paper compares four different fabrication methods for mercury cadmium telluride (HgCdTe) p-on-n devices. Among these methods, vertical liquid-phase epitaxy (VLPE) stands out because of its unique advantages, particularly the high activation rate of in situ arsenic (As) dopants. VLPE is an essential approach for producing high-performance p-on-n double heterojunction devices. This paper reviews the research progress, both domestically and internationally, covering material growth, device processes, and performance. The discrepancies between domestic and foreign research are discussed, and the key challenges and technical bottlenecks hindering VLPE technology development are identified. Several solutions have been proposed to solve this problem. This study provides insights into the future trends of VLPE technology for p-on-n heterojunction devices, which hold significant promise in semiconductor devices.