Ohmic contacts formed by electrodeposition and physical vapor deposition on p-GaN

Electrodeposited Pt and sputtered Ni/Pt contacts to p-GaN (p = 4.6 x 10(17) cm(-3)) are reported and compared to sputtered Ni, Pt, and Ni/Au contacts and electron beam and thermally evaporated Ni contacts. Sequential rapid th ermal annealing was employed with samples receiving an initial five minute heat treatment of 400 degrees C followed by 1 min anneals at 500, 600, and 700 degrees C, all under flowing N-2. Plots of current versus voltage for a ll contacts showed nonlinearity through the origin as deposited and for all annealing conditions. Extracted values of specific contact resistance are thus determined using the measured resistance for a given value of applied current. The lowest contact resistivity was reproducibly provided by the el ectrodeposited Pt contacts. After a 1 min anneal at 600 degrees C, a contac t resistivity of 1.50 x 10(-2) Ohm cm(2) was obtained using the circular tr ansmission line method at a measurement current of 10 mA. Sputtered Ni/ Pt contacts provided a contact resistivity of 1.81 X 10(-2) Ohm cm2 at 10 mA a fter a 1 min anneal at 600 degrees C, while all other metallizations yielde d contact resistivities from 3 - 4 x 10(-2) Ohm cm(2). Possible reasons for the lower contact resistivity of the electrodeposited contacts are discuss ed. (C) 1998 American Institute of Physics. [S0003-6951(98)02149-4].