Breakdown Voltage Enhancement of AlGaN/GaN HEMTs on Semi‐Insulating SiC Substrate by Optimizing Buffer Layer Structure

In this study, we discuss the effect of buffer layer structure parameters on breakdown voltage in AlGaN/GaN high electron mobility transistors (HEMTs) on semi‐insulating silicon carbide (SiC) substrate. We analyze the reasons for enhancing the breakdown voltage from the perspective of optimizing the electric field. Based on technology computer‐aided design (TCAD) simulation, the synergistic effect of the acceptor and donor traps in the buffer layer is analyzed. It is found that the space charge generated by its ionization can effectively weaken the peak electric field at the gate edge and suppress the electric field aggregation in the drain region, which significantly improves the voltage withstand performance. Furthermore, by investigating the thickness of the undoped channel layer, we discuss the effect of the distance between the carbon‐doped buffer layer and the channel on electric field relaxation. Finally, the thickness of the carbon‐doped buffer layer was changed to analyze the effect of the number of traps in the carbon‐doped buffer layer on the breakdown voltage, and the optimal thickness of the buffer layer was determined. After continuous optimization, AlGaN/GaN HEMTs with high breakdown voltage have been achieved without affecting the DC characteristics.