Very low resistance multilayer ohmic contact to n-GaN

A new metallization scheme has been developed for obtaining very low Ohmic contact to n-GaN. The metallization technique involves the deposition of a composite metal layer Ti/Al/Ni/Au (150 Angstrom/2200 Angstrom/400 Angstrom/500 Angstrom) on n-GaN preceded by a reactive ion etching (RIE) process which most likely renders the surface highly n type. Of the several attempts and with annealing at 900 degrees C for 30 s, contacts with specific resistivity values of rho(s) = 8.9 X 10(-8) Omega cm(2) or lower for a doping level of 4 X 10(17) cm(-3) were obtained. The physical mechanism underlying the realization of such a low resistivity is elucidated. (C) 1996 American Institute of Physics.