Optimization of Oxygen Plasma Treatment on Ohmic Contact for AlGaN/GaN HEMTs on High-Resistivity Si Substrate

The oxygen plasma surface treatment prior to ohmic metal deposition was developed reduce the contact resistance (RC) for AlGaN/GaN high electron mobility transistors (HEMTs) on a high-resistive Si substrate. plasma, which produced by an inductively coupled (ICP) etching system, has been optimized varying combination of radio frequency (RF) and ICP power. By using transmission line method (TLM) measurement, 0.34 Ω∙mm specific resistivity (ρC) 3.29 × 10–6 Ω∙cm2 obtained with conditions (ICP power 250 W, RF 75 0.8 Pa, O2 flow 30 cm3/min, 5 min), about 74% lower than that reference sample. Atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), photoluminescence (PL) measurements revealed large nitrogen vacancy, induced near treatment, primary factor in formation low contact. Finally, this integrated into HEMTs process, maximum drain saturation current 0.77 A/mm gate bias at 2 V HEMTs. Oxygen is simple efficient approach, without requirement additional mask or etch shows promise improve Direct Current (DC) performance