Thin films of II–VI compounds and alloys

Abstract

II–VI semiconductors and their alloys are promising thin film photovoltaic materials. Polycrystalline films of cadmium telluride (CdTe), zinc telluride (ZnTe), cadmium zinc telluride ($\text{Cd}{}_{\mathrm{x}}\text{Zn}{}_{\mathrm{1-x}}\text{Te}$), and mercury zinc telluride ($\text{Hg}{}_{\mathrm{x}}\text{Zn}{}_{\mathrm{1-x}}\text{Te}$) were deposited onto glass and transparent-conducting-semiconductor (TCS) coated glass substrates by metal-organic chemical vapor deposition. Emphasis was directed to the doping of CdTe films, ohmic contacts to p-CdTe, and thin film CdTe homojunctions. CdTe films may be doped intrinsically or extrinsically; gallium and arsenic were used as the extrinsic n and p dopant respectively. p⁺-ZnTe films deposited in situ were used as an ohmic contact to p-CdTe films. Thin film CdTe homojunctions were prepared by the successive in situ deposition of n-CdTe, p-CdTe, and p⁺-ZnTe films on SnO₂-coated glass substrates, and their properties were investigated. The properties of $\text{Cd}{}_{\mathrm{x}}\text{Zn}{}_{\mathrm{1-x}}\text{Te}$ and $\text{Hg}{}_{\mathrm{x}}\text{Zn}{}_{\mathrm{1-x}}\text{Te}$ films with band gap energy in the range 1.65–1.75 eV deposited onto glass and TCS-coated glass substrates were studied.