Abstract: The p-on-n HgCdTe infrared detector has advantages of long minority carrier life, low dark current, high R₀A product, and is an important device structure in the development of high-temperature detectors along with long wavelength infrared (LWIR) and very LWIR(VLWIR) detectors. However, there are few local reports on arsenic-implanted doped p-on-n long-wave HgCdTe detectors. To meet the urgent application requirements of high-performance long-wave detectors in the military and aerospace fields, studies have focused on long-wavelength p-on-n HgCdTe infrared detector annealing technology for As ion implantation. Secondary ion mass spectrometry(SIMS) was used to analyze the distribution of As ion concentration after implantation and annealing, and a semiconductor parameter tester was used to characterize the I-V characteristics of the pn junction. The results show that under mercury-rich conditions at 430℃ for 0.5 h and at 240℃ for 20 h, the As was activated. Further, the As implanted long-wavelength 15-μm 640×512 p-on-n HgCdTe infrared focal plane detector was successfully fabricated, and the operable pixel factor of the detector was greater than 99.7%. This research is of great significance for the fabrication of LWIR and VLWIR mercury cadmium telluride p-on-n focal plane detectors.