Schottky barrier height and surface state density of Ni/Au contacts to (NH4)(2)S-x-treated n-type GaN

By using capacitance-voltage and photoluminescence measurements, we have in vestigated the Schottky barrier height and surface state density of Ni/Au c ontacts to n-type GaN with, and without, (NH4)(2)S-x treatment. The Schottk y barrier height of 1.099 eV is very close to the Schottky limit of 1.10 eV for Au/Ni/n-type GaN treated with (NH4)(2)S-x. This result indicates that there is no severe Fermi level pinning induced by surface states. The reduc tion of the surface state density for the (NH4)(2)S-x-treated n-type GaN is attributed to the decrease of dangling bonds and occupation of nitrogen-re lated vacancies due to the formation of Ga-S bonds. (C) 2001 American Insti tute of Physics.