An extended investigation has been made of the electrical and photovoltaic properties of heterojunctions prepared by spray-pyrolysis deposition of thin ZnO films on single-crystal p-type CdTe. The principal experimental variables were the substrate temperature and the postdeposition temperature for annealing in H2. Under actual sunlight the optimum cell showed an open-circuit voltage of 0.54 V, a short-circuit current of 19.5 mA/cm2, and a solar efficiency (referred to the active area) of 8.8%, the highest value obtained to date for an authentic heterojunction on CdTe. The nature of the forward transport mechanism has been investigated, and a tunneling model in which bulk and interface deep traps control the forward characteristics is shown to provide good correlation with the experimental data.

Zinc oxide films were produced by spray pyrolysis starting with aqueous solutions of ZnCl2, ZnCl2 plus H2O2, and Zn acetate, and structural, optical, electrical, and thermoelectrical properties of the deposited films were investigated. Highly transparent films with resistivity as low as 10−3 Ω cm can be produced by suitable control of deposition procedures and by postdeposition annealing in hydrogen.

No abstract

Thin films of ZnSe deposited by vacuum evaporation have a high resistivity (≳5×108 Ω cm), even when donor impurities such as Ga or In and additional Zn are coevaporated. High-conductivity films of ZnSe were produced by annealing films, deposited with coevaporated Ga and Zn, in Zn vapor at 500 °C. Film resistivities in the range 0.5–40 Ω cm were obtained in this way, corresponding to degenerate n-type material with electron densities in the 1019-cm−3 range. Heterojunctions of n-ZnSe/p-CdTe and n-ZnSe/p-GaAs were investigated.

The structure of (100) silicon on (11̄02) sapphire is discussed for films grown by a special, defect-limiting process. A three-epitaxial-step technique, which utilizes both vapor phase epitaxy and solid phase epitaxy, is employed in the fabrication of low-defect-density films. The effects of different Si+ implantation energies and initial Si film thicknesses on the final structure of the film are investigated in order to optimize the electrical characteristics. The improvement in crystalline quality during the solid phase epitaxy step is due to overgrowth of the {221}-oriented microtwins by the [001) Si matrix. Both Rutherford backscattering spectroscopy and cross-sectional transmission electron microscopy are used in the analysis of the structure of these films.