| dc.description.abstract | This thesis is to investigate the gate characteristics of p-type GaN gated AlGaN/Ga N High Electron Mobility Transistor (HEMT), because p-type GaN can improve the energy barrier under the gate, effectively suppressing the gate current. It is known from the literature that electron and hole tunneling can be performed by thermal tunneling and Poole-Frenkel emission tunneling. Therefore, this experiment will measure the leakage current of devices at different temperatures. When the current is low positive bias, high positive bias and negative bias, the behavior of the carriers are found. When the positive bias is applied, the current will have two different slopes. It is known that there is hole injection and suppression of leakage at high bias. Current, then estimate the energy barrier value at each bias voltage. The energy barrier at high positive bias is about 0.7 V. The subsequent analysis of the gate capacitance changes with temperature at 1 MHz. It is found that the maximum value of the capacitance value decreases with temperature and will be occurs at higher bias, this mechanism is presumed to be related to the Schottky barrier of the gate electrode.
In general, due to the absence of an insulating layer on the gate, the gate bias of the high electron mobility transistor does not exceed 7 V. If an excessive voltage gate is applied, the carriers will not be able to withstand the traverse, resulting in weakly gate control, so this thesis will discuss the reliability of devices with high gate bias, observe the survival time of the devices under three kinds of bias, and use the numerical method of Weibull distribution to estimate the survival time of the devices during normal operation. Then, the temperature measurement was carried out to analyze the reliability and stability of the devices at different temperatures, and the change of the current before and after the high voltage stress was observed. It was found that the threshold voltage of the devices would have a negative shift in the high bias environment. Offset, and experimentally verified that there is a resistance current path between the gate and source of the device after the crash.
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