Low resistance Ohmic contacts to n-GaN by Ar plasma and forming gas ambient treatments

In this article, a scheme for fabricating low resistance Ohmic contacts to n-GaN was developed. This approach takes advantage of Ar plasma treatment and thermal annealing in forming gas ambient. As a result, the adjustment of Ar flow rate was very effective in improving the contact resistance. After proper Ar plasma treatment, the contact resistance and specific contact resistance of as-deposited Ohmic contacts were reduced to 0.362 Ω mm and 3.9×10^-5 Ω cm², respectively. Low contact resistance (0.103 Ω mm) and specific contact resistance (3.2×10^-6 Ω cm²) were obtained after annealing in N₂ gas ambient. By performing thermal annealing in forming gas ambient, even lower contact resistance (0.093 Ω mm) and specific contact resistance (2.6×10^-6 Ω cm²) were successfully achieved, indicating that the electrical characteristics of Ohmic contacts would not be affected by the effect of hydrogen passivation of dopants in n-GaN. © 2003 American Vacuum Society.