Control of defects and impurities at GaN and AlGaN surfaces for FET and sensor applications

The authors proposed a surface control process using ultrathin Al layer for suppressing surface donor states at AlGaN. The Ni/Au Schottky diodes fabricated on the processed AlGaN surfaces showed pronounced reduction of leakage current and clear temperature dependence of I-V curves. The AlGaN/GaN HFETs fabricated with surface control showed remarkable reduction of gate leakage currents and the improvement of stability of drain currents against high-temperature/current stress. The surface process also brought a significant decrease in dark current in the Pd/AlGaN/GaN H₂ sensor. The Pd/AlGaN/GaN diode showed the systematic shift in the C-V curve for different partial pressure of H ₂. The maximum shift in the threshold voltage obtained was about 1200 mV which is much larger than 500 mV reported for the Pd-based Si MOS sensors