Ohmic contact to p-type GaN with the lowest contact resistivity was de
veloped by the surface treatment prior to Pd/Au metal deposition. The
contact resistivity drastically decreased from 2.9 x 10(-2) to 4.3 x 1
0(-4) Ohm cm(2) by the surface treatment using aqua regia. The surface
treatment plays a role in removing the surface oxide formed on p-type
GaN during epitaxial growth, and subsequently in reducing the barrier
height for holes at the interface of Pd/ p-type GaN, resulting in the
good ohmic contacts to p-type GaN. (C) 1998 American Institute of Phy
sics. [S0003-6951(98)01246-7].