Ohmic Contact to n-GaN Using RT-Sputtered GaN:O

One of the key issues in GaN-based devices is the resistivity and technology of ohmic contacts to n-type GaN. This work presents, for the first time, effective intentional oxygen doping of sputtered GaN films to obtain highly conductive n⁺-GaN:O films. We have developed a novel and simple method to obtain these films. The method is based on the room temperature magnetron sputtering of a single crystal bulk GaN target doped with oxygen. The n⁺-GaN:O films exhibit a polycrystalline structure with a crack-free surface and a free electron concentration of 7.4 × 10¹⁸ cm³. Ohmic contact to GaN:Si with n⁺-GaN:O sub-contact layer achieves specific contact resistance of the order of 10^-5 Ωcm² after thermal treatment. The obtained results are very promising for the development of the technology of a whole new class of ohmic contacts to n-GaN.