Metallisation induced electron traps in epitaxially grown n-type GaN

Sputter deposition is a versatile method of depositing metal layers onto semiconductors, but it introduces electrically active defects at and below the semiconductor surface. We have used deep level transient spectroscopy (DLTS) to study the electrical properties of defects, ES1–ES4, introduced in epitaxial n-GaN during sputter deposition of Au Schottky contacts. Two of these defects, ES1 and ES2, located at EC−0.22±0.02 eV and EC−0.30±0.01 eV, respectively, exhibit a metastable-like behaviour. ES1 and ES2 can both be removed under a zero bias annealing at temperatures of as low as 20 K and are re-introduced during reverse bias annealing at temperatures of 100–125 K and 115–140 K, respectively. The re-introduction of ES1 was found to follow first order kinetics with an activation barrier of (0.22±0.02) eV.