Zn3P2 thin films grown on glass substrates by MOCVD

Abstract

Zinc phosphide (Zn3P2) polycrystalline thin films have been grown by low-pressure metalorganic chemical vapor deposition on glass substrates. Electrical properties have been evaluated for the films grown at growth temperatures from 200 to 400°C and with the P/Zn molar ratio fixed at 5.7. The growth of Zn3P2 is limited by surface reaction at growth temperatures below around 240°C and by mass transfer from the gas phase to the surface at 260–380°C. The preferential orientation along the c-axis became dominant at 260–290°C. The rate for decomposition of Zn3P2 and the gas-phase reaction had to be considered above around 390°C. The electrical conductivity of the films was found to increase with raising growth temperature. From the temperature dependence of electrical conductivity, four levels were obtained with activation energies of 0.06 eV, 0.16 eV, 0.21 eV and 0.66 eV for the Zn3P2 films. The concentration of levels increased as the growth temperature was raised.