Preparation and characterization of ZnO thin films on InP by laser-molecular beam epitaxy technique for solar cells

Abstract

Highly c-axis oriented ZnO thin films were epitaxially grown on semi-insulating 〈1 0 0〉 oriented InP substrates (SI-InP) held at room temperature (RT), 200°C and 300°C by laser molecular beam epitaxy (L-MBE) i.e., pulsed laser deposition. Through X-ray diffraction analysis, the material, the crystalline quality and the epitaxial lattice matching of the film were confirmed. The obtained high intense peak shows that the most preferential orientation was (0 0 2), i.e; along the ‘ c-axis’. Results obtained from the optical studies indicated that the deposited film showed nearly 95% transparency and acts as anti-reflection medium. Photoluminescence (PL) study confirms the high electrical conductivity of the film and the obtained low-intensity PL spectrum indicates high O/Zn ratio. Further, the elemental peaks for Zn, O, In and P were identified by EDAX and the spectrum shows the stoichiometry of the ZnO thin films. From the optical absorption spectrum, the optical band gap and the thickness were calculated. The sheet resistance of the deposited ZnO thin films was measured for various deposition temperatures. Structural, compositional, surface morphological, optical and photoluminescence characterization results are discussed.