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This study discusses the application of the substrate voltage during the recovery time with the dynamic on-resistance (dynamic ${R}_{\text {on}}$ ) method to extract the deep trap states in the buffer layer after the hard-switching stress in p-GaN high electron mobility transistors (p-GaN HEMTs). This method will be more suitable for the detection of the deep trap states where the carriers are difficult to de-trap in the buffer layer. Then, a hard switching stress condition is applied to the device and the degradation is caused by the mechanism of the hot electron effect and the impact ionization. The generated electrons and holes will trap into the buffer layer in the drift region at the gate edge near the drain side and the AlGaN layer under the gate, respectively. Moreover, through the novel of the dynamic ${R}_{\text {on}}$ method with the substrate voltage applied, the deep trap states in the buffer can be extracted.

This work proposes forming-free HfO2-based resistance random access memory (RRAM) using X-ray irradiation which overcomes the bottleneck of the conventional forming process, that of the need for a larger forming voltage with scaling. In addition, a large irradiation area is beneficial to the mass production of memory devices. This forming-free device has a better memory window compared to the device without X-ray irradiation. Moreover, the forming-free device has good reliability as the device without X-ray irradiation. To analyze the physical mechanism, the conduction mechanism was investigated by the current-fitting technique, and irradiation experiments with varying X-ray energies and times were performed. Finally, a physical model is proposed to explain the mechanism of the forming-free RRAM from X-ray irradiation.