GaN nanowires doped with silicon were grown on Si(111) substrates by catalyst-free molecular beam epitaxy (MBE). Contacts were fabricated to single nanowires with a Ti/Al metallization scheme. Low-resistance ohmic contacts were achieved after annealing for 60 seconds at 500 ?C in 5 % hydrogen and 95 % argon ambient. Using current-voltage curves to determine the resistance of several wires from each growth run and SEM to measure the dimensions, we were able to calculate a specific contact resistivity for nanowires with different doping densities. A growth run consisting of highly doped wires had a specific contact resistivity of 1.9 x 10-5 Ω-cm2. We also estimated a bulk resistivity of approximately 0.003 Ω-cm and a free carrier concentration in the nanowires on the order of 1.5 to 2 x 1019 cm-3. Moderately doped nanowires had a higher specific contact resistivity of 3.5 x 10-4 Ω-cm2, an estimated bulk resistivity of 0.01 Ω-cm, and a free carrier concentration on the order of 3.5 x 1018 cm-3.
Proceedings Title: Proc., International Conference of Nitride Semiconductors
Conference Dates: September 16-21, 2007
Conference Location: Las Vegas, NV
Conference Title: International Conference of Nitride Semiconductors
Pub Type: Conferences
contact resistance, GaN, molecular beam epitaxy, nanostructures, nanowires, nitrides, resistivity