Formation of high-quality Ni/Ag contacts on p-GaN/AlGaN/GaN platform

This study systematically investigated Ni/Ag contacts for moderately doped p-GaN/AlGaN/GaN heterostructure, including contact optimization, the conduction formation mechanism, and the carrier transport model. High-quality Ni/Ag (1/120 nm) contacts were achieved with a low contact resistance (11.24 Ω·mm at ± 5 V), a low contact resistivity (2.64 × 10⁻⁵ Ω·cm²) and a low roughness surface topography (14.4 nm). Furthermore, based on the thermionic field emission (TFE) model for Ni/Ag (1/120 nm), the Schottky barrier height (SBH) was extracted as 1.04 eV, the interfacial carrier concentration was 1.8 × 10²⁰ cm⁻³ and the depletion width was 2.46 nm. The thin barrier width promoted field emission, which led to a low contact resistance.