Defect Characterization of Multicycle Rapid Thermal Annealing Processed p-GaN for Vertical Power Devices

Abstract

Post-implantation damage and defect characterization of multicycle rapid thermal annealing (MRTA) activated Mg+ implanted (0001) GaN on (110) sapphire substrate was investigated using high resolution X-ray scattering and transmission electron microscope techniques. The initial implant-induced isolated defects produced a pseudomorphic strain that matches the calculated recoil damage profile in the GaN - along the [0001] direction. Triple axis X-ray diffraction showed removal of the implant-induced elastic strain during two different MRTA annealing processes. An improvement in crystalline quality after the different MRTA processes was also noted, indicating that the MRTA processes can reduce crystalline strain and defects in as-grown material. For the different MRTA processes, an improvement in electrical conductivity was correlated with a lower (0004) triple axis rocking curve width and with a reduced presence of extended defects observed from electron microscopy measurements. The extended defects were identified to be circular defects with an observable screw component. The defect density was on the order of 1010 cm−2. While both MRTA processes led to a high activation efficiency, a higher residue defect density was correlated with a greater X-ray scattering rocking curve width of the symmetric (0004) reflection, which was further correlated with a lower hole mobility (20 cm2/V⋅s vs 40 cm2/V⋅s).