Low-resistance and nonalloyed ohmic contacts to epitaxially grown n-ZnO wer
e fanned by exposing n-ZnO to an inductively coupled hydrogen and an argon
plasma. Using Ti/Au, the specific contact resistivity of the ohmic contact
was drastically decreased from 7.3 X 10(-3) to 4.3 X 10(-5) Ohm cm(2) by hy
drogen plasma treatment. The photoluminescence spectrum of the hydrogen pla
sma treated ZnO showed a large enhancement in band-edge emission and a stro
ng suppression in deep-level emission. These results suggest that the low c
ontact resistivity can be attributed to an increase in carrier concentratio
n on the ZnO surface. The specific contact resistivity of the Ar-plasma tre
ated sample was also decreased to 5.0 X 10(-4) Ohm cm(2), presumably due to
the information of shallow donor on the ZnO surface by ion bombardment. (C
) 2001 American Institute of Physics.