Excimer Laser Enhancement And Probing Of 111-V Compound Semiconductor Chemical Vapor Deposition

Abstract

InP and In203 have been deposited on GaAs, and InP ,ubstrates by excimer laser induced photodecomposition of (CH3)3InP(CH3)3 and P (CH3) 3 vapors at 193 nm. Phosphorus incorporation in the films was greatly enhanced by focusing the laser beam to promote multiple-photon dissociation processes. These conditions also lead to enhanced carbon inclusion in the films, due to formation of species such as CH and CH2 in the gas-phase. However, this carbon inclusion could be suppressed by focusing the beam onto the surface at normal incidence. The technique offers several potential advantages over conventional metal-organic chemical vapor deposition (MOCVD), including lower temperature, enhanced rates, safer gases, and three-dimensional film composition control. Strong atomic In emission is observed in the gas-phase above the depositing film, due to a multiple photon dissociation process. Gas-phase fluorescence from P, CH, and C was also observed. These emissions give insight into the photodecomposition mechanism and also serve as a monitor of metal organic precursor concentrations. In addition, excimer laser excitation has been used to detect PH3, P2, AsH3, As2, InCI, and GaC1 in a reaction tube designed to simulate a conventional CVD growth reactor. These are the primary reactants participating in the chemical vapor deposition (CVD) of InP/InGaAsP epitaxial layers. Detection limits for all these species are well below those levels typically employed during layer growth.