The current-voltage and spectral response characteristics of arsenic-doped base region long-wavelength HgCdTe n-on-p planar photodiode are reported in this paper.The arsenic-doped base region long-wavelength HgCdTe n-on-p planar photodiode was compared and analyzed with Hg vacancy long-wavelength HgCdTe n-on-p planar photodiode,and it was found that the performance of the former was superior to the latter,such as the R0A products,the current responsivity,and the blackbody detectivity.