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

Electrodeposited Pt and sputtered Ni/Pt contacts to p-GaN (p=4.6×1017 cm−3) are reported and compared to sputtered Ni, Pt, and Ni/Au contacts and electron beam and thermally evaporated Ni contacts. Sequential rapid thermal annealing was employed with samples receiving an initial five minute heat treatment of 400 °C followed by 1 min anneals at 500, 600, and 700 °C, all under flowing N2. Plots of current versus voltage for all 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 electrodeposited Pt contacts. After a 1 min anneal at 600 °C, a contact resistivity of 1.50×10−2 Ω cm 2 was obtained using the circular transmission line method at a measurement current of 10 mA. Sputtered Ni/Pt contacts provided a contact resistivity of 1.81×10−2 Ω cm2 at 10 mA after a 1 min anneal at 600 °C, while all other metallizations yielded contact resistivities from 3–4×10−2 Ω cm 2. Possible reasons for the lower contact resistivity of the electrodeposited contacts are discussed.