The transport properties of conventional Au-based low-resistance ohmic
contacts to n- and p-type InP have been investigated. For n-type InP,
a good agreement between the minimum specific contact resistance and
the bulk doping density is observed in accordance with an inverse bulk
doping density dependence for the specific contact reistance. Drift a
nd diffusion across a thermodynamically stable metalphosphide-InP junc
tion is found to be the rate-limiting step of the low-resistance conta
cts to n-type InP. Tunneling is not observed, but rather a significant
ly effective Schottky barrier lowering is initially responsible for th
e low-resistance contacts. Significant Schottky barrier lowering is al
so observed for ohmic contacts to p-type InP, but no total transition
from predominately thermionic emission to drift and diffusion is obser
ved for low-resistance contacts to p-type InP, indicating that the con
tacts are not fully developed, and that further reduction of the speci
fic contact resistance can be expected.