Improving metal/semiconductor conductivity using AlOx interlayers on n-type and p-type Si

Thermal atomic layer deposition was used to form ultra-thin interlayers in metal/interlayer/semiconductor Ohmic contacts on n-type and p-type Si. AlOx of thickness 1-2 nm was deposited at 120 degrees C on Si substrates prior to metallization, forming Ni/AlOx/Si contacts. Conductivity improved by two orders of magnitude but the contacts remained rectifying. When they were annealed at 200 degrees C, the conductivity increased by another order of magnitude and the samples became Ohmic. A minimum specific contact resistivity of 1.5 x 10(-4) Omega-cm(2) was obtained for structures based on lightly doped (10(15) cm(-3)) Si substrates. Existing models that describe Fermi level de-pinning do not fully explain our results, which are however consistent with other experimental data in the literature. (C) 2014 AIP Publishing LLC.