Ni/Pd-based ohmic contacts to p-GaN through p-InGaN/p+-GaN contacting layers

Abstract

Specific contact resistance to p-GaN was measured for various structures of Ni/Pd-based metals and thin (20–30 nm thick) p-InGaN/p+-GaN contacting layers. The effects of surface chemical treatment and annealing temperature were examined. The optimal annealing temperature was determined to be 550 °C, above which the sheet resistance of the samples degraded considerably, suggesting that undesirable alloying had occurred. Pd-containing metal showed ~35% lower compared to that of single Ni. Very thin (2–3.5 nm thick) p-InGaN contacting layers grown on 20–25 nm thick p+-GaN layers exhibited one to two orders of magnitude smaller values of compared to that of p+-GaN without p-InGaN. The current density dependence of , which is indicative of nonlinearity in current-voltage relation, was also examined. The lowest achieved through this study was 4.9 × 10–5 Ω·cm2 @ J = 3.4 kA/cm2.