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As a transmitter power amplifier (PA), the electrical output characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs) are closely related to the drain current versus drain voltage (${I}_{d}$ – ${V}_{d}$) characteristics. Any abnormalities in the ${I}_{d}$ – ${V}_{d}$ characteristics will seriously affect device performance. Therefore, many groups have investigated the kink effect of GaN HEMTs. One of the commonly used measurement methods of the kink effect is the ${I}_{d}$ – ${V}_{d}$ forward and reverse sweep. In this study, we used the same method for Al2O3/Si3N4–AlGaN/GaN metal–insulator–semiconductor HEMT (MIS HEMT) devices. We found that not only did the kink effect occurred but ${I}_{d}$ also increased abnormally during the reverse sweep and after a series of electrical measurements. At the end of the forward sweep, impact ionization caused by a high ${V}_{d}$ generated electron–hole pairs and some holes accumulated under the gate region, which caused the negative shift of the threshold voltage (${V}_{\text{Th}}$), leading to an abnormal increase in ${I}_{d}$ during the reverse sweep. [ABSTRACT FROM AUTHOR]

According to previous research, supercritical fluid nitridation (SCFN) treatment yields only a limited improvement in AlGaN/GaN high-electron-mobility transistors due to the additional water molecules generated during the SCFN treatment, which reacts with dangling bonds of AlGaN/GaN causing undesirable oxidation, thereby affecting the reliability of the device. In this study, we performed an annealing (ANL) treatment post the SCFN treatment to obtain an ANL-SCFN device with improved electrical performance, owing to the fact that the ANL treatment decreases the gate current leakage and increases the reliability of the device. Furthermore, to verify the decrease in the number of defects in the AlGaN layer of the device after ANL, we conducted a reliability analysis of the negative bias voltage stress (NBS) to observe the deterioration in the output of the device. Previous studies state that the electrons generated through NBS trap the defects in the AlGaN layer, thereby decreasing the electrical properties of the device. However, this study showed that the degradation of the ANL-SCFN device reduced significantly after the NBS analysis, considering the amount of OFF-state leakage decreased due to the ANL treatment, which improved the switching characteristics of the device. [ABSTRACT FROM AUTHOR]

In the past, gate turn-off (GTO) thyristors were commonly used to either increase the length of the drift region or reduce the doping concentration to increase high-voltage and high-power applications. However, this results in an on-resistance (Ron) increase. In this study, we applied a supercritical fluid (SCF) treatment to devices which has the advantage of high permeability and low-temperature processing to passivate SiC-GTO bulk defects. After the proposed defect passivation, the breakdown voltage has been improved by 8% without increasing on-state resistance. In addition, the leakage current has also been suppressed more than 30% in average. This study also uses electrical analysis to understand the characteristics of the devices after SCF treatment, and then discusses the passivation mechanism of materials of the devices from this treatment. [ABSTRACT FROM AUTHOR]