Surface states passivation in GaN single crystal by ruthenium solution

Abstract

GaN single crystal samples were cleaned and passivated with ruthenium solution. Photoluminescence (PL) and scanning tunneling spectroscopy (STS) were used to characterize the passivated surface. PL study showed an effective increase in band edge emission after passivation. I–V (current–voltage) and dI/dV (differential conductance) spectra measurements of GaN single crystal samples using ambient STS revealed the variation in the density of states (local), shifting of Fermi-level position, and onset/offset of valence and conduction bands. We found a significant change in I–V and dI/dV measurements after surface treatment, which means modification in surface electronic properties. The ruthenium solvent passivates the surface states, converting the surface into a highly ordered and air oxidation-resistant state. Finally, Ni/GaN Schottky diodes were fabricated to demonstrate improved device characteristics after passivation, which was a direct indication of improved GaN interface due to ruthenium passivation.