Distinct junction transformations of pixel-arrayed long-wavelength infrared detectors by photocurrent mapping

Abstract

Pixel-arrayed long-wavelength HgCdTe is of great significance in the development of infrared detection. However, the PN junction formation process for long-wavelength HgCdTe is complex. The damage induced by boron ion implantation and subsequent low-temperature annealing may results in changes in the effective doping concentration and geometry of the actual n-type implantation region. Therefore, an in-situ, non-destructive scanning-photocurrent-microscopy (SPCM) method is needed to test the performance and electroactive defects of HgCdTe devices. Here, the pixel-arrayed long-wavelength infrared detectors with n-on-p structure formed by B+ ion implantation in Hg vacancy-doped Hg0.78Cd0.22Te crystals were fabricated. The SPCM method is used to characterize the PN junction performance of long-wavelength Hg0.78Cd0.22Te array detectors. It is found that the long-wavelength device transformed from n-on-p structure to n-on-n− structure at about 175 K, and further turns into an n−-on-n-on-n− structure with the temperature increasing. In addition, when the temperature increases, the minority carrier diffusion length in the B+ ion implantation region gradually decreases with the activation of the recombination center. Our work provides an effective theoretical and experimental basis for the HgCdTe junction formation process.