Electrical characteristics of n-GaN Schottky contacts on cleaved surfaces of free-standing substrates - Metal workfunction dependence of Schottky barrier height

摘要

We report electrical characteristics of Schottky contacts with 9 different metals (Ag, Ti, Cr, W, Mo, Au, Pd, Ni, Pt) formed on clean m-plane surfaces by cleaving free-standing GaN substrates, comparing with the contacts on Ga-polar c-plane n-GaN surfaces grown on GaN substrates. The n-values in the forward current-voltage (I-V) characteristics are as good as 1.02 to 1.05 for the m-plane and 1.02 to 1.09 for the c-plane samples. We found that the reverse I-V curves of the both samples can be explained with the thermionic field emission theory, and the m-plane contacts have a metal work-function dependence of Schottky barrier heights as large as that of the Ga-polar c-plane n-GaN contacts. These results tell us that the cleaving method can provide the clean m-plane surfaces where Fermi-level pinning is as small as those of the c-plane.