Excimer laser-induced deposition of InP: Crystallographic and mechanistic studies

Abstract

InP thin films have been deposited on several types of substrates via 193-nm excimer laser-induced photochemical decomposition of (CH3)3In and P(CH3)3 gas-phase precursors. The characteristics of the deposited films are studied over a wide range of conditions. A photochemical model is proposed which explains the stoichiometry and rate at which the film deposits. Approximate fluences are given for the onset of (in order of increasing fluence) In-precursor photochemistry, P-precursor photochemistry, CHx photochemistry, laser-induced crystallization, and laser damage. Crystallinity of InP films deposited on (100) InP substrates has been studied by scanning electron microscopy, transmission electron microscopy, and Rutherford backscattering spectroscopy. Films range from amorphous to epitaxial, depending upon conditions (most notably fluence incident on the substrate). The best film deposited at ∼0.1 J/cm2 and at a steady-state temperature of only ∼320 °C had a backscattering spectrum indistinguishable from that of the substrate single crystal. To our knowledge, this is the first report of a 100% photochemically-induced deposition of an epitaxial, III-V compound semiconductor thin film (i.e., no growth in the absence of light), and also the first report of an epitaxial InP film deposited from organometallic precursors at a steady-state temperature below the incongruent decomposition temperature of InP (∼350 °C).