Disclosing the carrier distributions in ion-implanted HgCdTe p–n junctions with scanning capacitance microscopy

Ion implantation doping is the primary method for forming p–n junctions in HgCdTe. However, the doping and activation in HgCdTe are influenced by various complex factors, leading to inconsistencies between the actual carriers and the distribution of impurities. Currently, there are few experimental reports on nanoscale carrier distribution in HgCdTe photovoltaic structures. In this study, we employed scanning capacitance microscopy (SCM) to obtain the nanoscale dC/dV profiles on the cross-section of HgCdTe diodes, which refer to the distributions of electrons and holes in the junction region. The depletion area of the p–n junction was then identified precisely according to the measurement. For the arsenic-implanted p-on-n structure, the electrical distribution is highly consistent with that of the dopants. In contrast, for the n-on-p structure, the SCM study reveals the formation of n−–p and p–p regions instead of the simple n+-p junction by heat treatment after boron-ion implantation; both are believed to play key roles in achieving optimal performance of HgCdTe photodetectors. Our study provides a direct approach to uncover the spatial distribution of carriers in the HgCdTe p–n junction, which is crucial in determining the electrical and photoelectric properties of the diodes.