Chemical Vapor Deposited Tungsten Film on Molecular Layer Epitaxially-Grown GaAs and its Application to Low Resistivity Contact

Abstract

ABSTRACTW CVD process was caried out on molecular layer epitaxially-grown GaAs just after in-situ surface treatment under optimized AsH3 pressure followed by ex-situ photolithography process. The precursor for W CVD used is W(CO)6. The W/GaAs interface is analyzed using SIMS and RBS/channeling technique. Interface structure was directly observed by cross sectional HRTEM. Plan view HRTEM observation was also carried out. From these physical analyses, it is shown that the mixed layer at W/GaAs interface is estimated to be about 2–3 ML and that the deposited W layer is epitaxially aligned with underlying GaAs lattice. The contact resistance in W/GaAs is obtained by the transmission line measurements (TLM) of patterned W on heavily doped GaAs grown by (molecular layer epitaxy) MLE. The dependence of the contact resistance on the surface treatment prior to the W CVD is also studied. Barrier height of W/GaAs structure is measured by the temperature dependence of I-V characteristics. Contact resistance of non-alloyed structure achieved are 3 × 10−7 Ωcm2 for n-type GaAs:Te and below 5 ×10−8 Ωcm2 for p-type GaAs:C respectively.