Low temperature formation of low resistivity W contact with ultra thin mixed layer on molecular layer epitaxially-grown GaAs

The precursor for the W CVD on GaAs used is W(CO)₆. The contact resistance in W/GaAs is obtained by the transmission line measurements of patterned W on heavily doped GaAs grown by 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 in reference to the contact resistance. The W/GaAs interface is analyzed using SIMS and RBS. Contact resistance of non-alloyed structure achieved are 3×10^-2 Ω cm² for n-type GaAs and below 5×10^-8 Ω cm² for p-type respectively. From the physical analysis, the mixed layer in W/GaAs interface is estimated less than 20 Å