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 $870~^{\circ }$ C, the specific contact resistivity and contact resistivity of Ni/Au metal stack decreased from $1.3\times 10^{-{3}}~\Omega \cdot $ cm2 to $1.2\times 10^{-{4}}~\Omega \cdot $ cm2 and from $78.2~\Omega \cdot $ mm to $22.5~\Omega \cdot $ 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 GaOX 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.