RF sputtered films of Cu-doped and N-doped ZnTe

Polycrystalline thin film solar cells using the CdS/CdTe structure have good efficiencies but the ideal low resistance ohmic contact to the p-type CdTe which is stable has yet to be developed. A good candidate for this contact would be p-type ZnTe produced by sputtering, which is a process that is scalable to large areas. We have successfully doped ZnTe with copper and nitrogen using RF planar magnetron sputtering. For the copper doping, resistivities as low as 0.01 ohm-cm have been achieved. Raman spectra have been used as an indicator of film quality. Nitrogen doping was achieved by introducing small amounts of molecular nitrogen into the argon sputter gas during ZnTe deposition. A minimum film resistivity of about 20 ohm-cm was obtained for films grown using approximately a 5% N₂/Ar ratio at a pressure of 18 mTorr and a substrate temperature in the vicinity of 400 C. Here, again, Raman spectra were used to check on film quality by comparing to that of pure ZnTe