Low-Resistivity Ohmic Contact on p-GaN/AlGaN/GaN Enabled by Mg-Doped Spin-on-Glass Treatment

Mg-doped spin-on-glass (SOG) treatment is employed as a simple and effective Mg doping method, which can lower the barrier height of p-GaN/metal and form robust Ni/Au Ohmic contact on p-GaN/AlGaN/GaN structure. After SOG treatment annealed at 870°C, the specific contact resistivity and contact resistivity of Ni/Au metal stack decreased from 1.3 × 10⁻³ Ω·cm² to 1.2 × 10⁻⁴ Ω·cm² and from 78.2 Ω·mm to 22.5 Ω·mm, respectively. The SOG treatment maintained a good surface morphology and effectively increased Mg concentration near the p-GaN surface, which could in situ decompose the dense GaO_X layer. In addition, the SOG treatment facilitated Ga out-diffusion from p-GaN layer, and the inversion process induced by Ni/Au-based p-GaN Ohmic annealing is more complete, ultimately forming a p-GaN/Au/NiO Ohmic stack with a favorable atomic arrangement interface. These results demonstrate the significant potential of SOG technology in the selective doping of p-GaN.