Fabrication and electrical characteristics of Ti/Al ohmic contact to Si⁺ implanted GaN

Abstract

Ti/Al ohmic contact with an extremely low specific contact resistance has been formed by the deposition of Ti and Al films on Si+ lanted GaN. The ohmic contact formed by annealing at 600 o C of Ti film with a thickness of 50 nm and Al film with a thickness of 200 nm reveals the good smooth surface and uniform structure as compare to those of contacts formed above 700 °C, which is correlated to whether the Al-Ti alloy is melted during the annealing of ohmic contact or not. The specific contact resistance of 2 × 10-6Ω-cm2 is obtained for Si+ implanted GaN with a dose of 5 × 1013 cm-2. As Si ion dose increases to 5 × 1014 /cm2, the specific contact resistance is reduced to 2 × 10-8 Ω-cm2. It is revealed that the selective doping at high impurity concentration in the surface region by Si+ implantation is useful to reduce the contact resistance for Ti/Al contact to GaN.

Lateral GaN MISFETs Fabricated in Mg Ion Implanted Layer

“…We selected the annealing temperature of 550 °C because the surface concentration of Si ions implanted regions was very high (near 3 × 10 20 cm -3 ). The annealing of Ti/Al layers at 550 °C resulted in the smooth and uniform structure of Ohmic contact and gate electrodes and getting low Ohmic contact resistance of 2 × 10 -8 ohm-cm 2 [10,11].…”