Surface passivation of CdZnTe wafers

The chemical polishing process and the subsequent passivation process of CdZnTe wafers were studied. The treatment effects were tested through XPS analysis and I-V measurement. The chemical etching in 2%Br-MeOH solution may effectively remove the damaged layer and improve the ohmic contact between CdZnTe wafer and Au electrodes. CdZnTe wafers after Br-MeOH etching were passivated with five different passivants respectively. It was found that the surface leakage currents of all CdZnTe wafers passivated with different passivants were reduced by 1-2 orders. CdZnTe wafer passivated in NH₄F/H₂O₂ solution showed the best passivation efficiency because the enriched Te on the surface was fully oxidized to TeO₂, which results in the thickest oxide layer, the most stoichiometric surface and the least leakage current. The surface of CdZnTe wafer is Te-rich after passivated in NH₄F/H₂O₂ or H₂O₂ solution and Cd-rich after passivated in KOH or KOH/H₂O₂ solution.