Radiation induced defects in MOVPE grown n-GaN

It is well known that exposure of semiconductor surfaces to energetic particles introduce both optically and electrically active defects. Hydrogen and He-ion implantation has been used in GaN-based microelectronic processes. He-ion implantation produced high resistivity GaN at a fluence that is compatible with photoresist masking techniques. Heavier ion implantation has the added advantage that the depth resolution of the incident ions can be ‘tuned’ for specific applications (lifetime tailoring, etc.). Using deep level transient spectroscopy the defects in as-grown n-GaN as well as those introduced during high energy proton, He-ion and electron bombardment are characterised. Prior to irradiation, four electron defects (EO1–EO3 and EO5) were observed in the as-grown GaN. Two defects ER1 and ER2, not previously observed after electron irradiation, were observed after high energy electron irradiation. He-ion, proton and electron irradiation introduced a defect ER3. Defects ER1 and ER2 were also observed after proton bombardment, whereas two deeper lying defects (ER4 and ER5) were observed after the He-ion bombardment. The electronic properties, introduction rates and the annealing kinetics of the particle induced and as-grown major defects are presented. The influence of defect removal on the Schottky barrier diode properties are also discussed.