Study of Oxygen Implantation in GaN/Sapphire

Abstract

This paper presents the effect of oxygen implantation in MOCVD grown GaN epitaxial layer on sapphire substrate. Oxygen implantation was done on three different energies with different dose, namely 3 × 10¹⁴ cm⁻² at 30 keV, 5 × 10¹⁴ cm⁻² at 60 keV and 1.2 × 10¹⁵ cm⁻² at 100 keV in the same GaN sample to get a flat impurity doping profile. Implanted sample was characterized by High Resolution X- ray Diffraction (HRXRD), Field Emission Scanning Electron Microscopy (FE-SEM) and wet chemical etching. Sample was also annealed at 800 °C, in air, for 5 min duration to reduce the implantation damage. Break down voltage of the sample was also measured before and after annealing to see the suitability of implantation process for device isolation. The breakdown voltage showed an increase after the implantation and annealing. The increase in the breakdown voltage has been explained in terms of the increase in the defect density as a result of the implantation. Increasing the breakdown voltage is attributed to trapped charge carrier by the defective region thereby increasing resistivity. Wet chemical etching of the samples were done to determine the dislocation density before and after implantation. Increase in the dislocations is also inferred to increase the resistivity in the sample.