GaN-Passivation of GaAs with Less Plasma Damages: Effects of Input Plasma Power, Substrate Heating and Post-Thermal Annealing

Abstract

In order to achieve the plasma-damage-free GaN passivation of GaAs, GaAs (100) substrates were nitrided in helicon-wave-excited N2–Ar plasma with reduced input plasma power (260 W → 180 W) and substrate heating at 200°C together with the post-thermal annealing in N2 ambient. The current-density–voltage (J–V) characteristics of Schottky or tunnel metal-insulator-semiconductor (MIS) diodes were measured to evaluate the effects of the reduced plasma damage and the extent of the passivation. The reverse leakage current decreased substantially as the input plasma power was reduced from 260 W to 180 W. Substrate heating at 200°C and the post-thermal annealing in N2 ambient were also effective in diminishing the reverse leakage current. The extent of the decrease in the carrier density observed near the GaN/GaAs interface was also improved by the above treatment. The thermal stability was also greatly improved by GaN passivation. The ideality factor and Schottky barrier height did not show any degradation up to the annealing temperature (of the diode samples) of as high as 500°C. The J–V characteristics did not show any deterioration for the GaN-passivated GaAs samples even after long-time (3–16 months) exposure to air, while they showed remarkable degradation for the untreated GaAs sample after air exposure of only 3 weeks.