Sodium-doping of ZnTe film by close-spaced sublimation for back contact of CdTe solar cell

Low resistivity p-type ZnTe film was formed by close-spaced sublimation utilizing sodium compounds as sodium source for doping. Sodium was incorporated during film deposition with ZnTe sources containing various amount of Na2Te, Na3PO4, or NaCl. Film resistivity of less than 1 Ω cm with hole concentration of 6 × 1017 cm−3 was achieved by doping with Na2Te. However, doping with Na3PO4 or NaCl was less effective in reducing the resistivity of ZnTe film due to low carrier concentration. Hole mobility was correlated with the microstructure of the ZnTe film, which strongly depends on the kind and content of sodium compound in the source.