10 kV E-mode GaN HEMT: Physics for breakdown voltage upscaling

High-voltage GaN high electron mobility transistors (HEMTs) have recently reached the 10 kV milestone; however, prior reports relied on unconventional epitaxial structures—such as multi-channel, Si delta-doping, or unintentional p-GaN doping—which pose challenges in the realization of enhancement-mode (E-mode) gate control. Here, we demonstrate a 10 kV E-mode GaN HEMT with a standard highly doped p-GaN gate. This p-GaN layer also forms a reduced-surface-field (RESURF) structure. By analyzing devices with varying RESURF thickness (t_R), we identify the key physical mechanism that enables the breakdown voltage (BV) upscaling with device length. We find the BV upscaling is only viable when t_R is below 21 nm and reaches peak effectiveness at a t_R of 17 nm—deviating from predictions based on ideal polarization superjunction theory. This suggests the presence of donor trap states that balance the acceptors in p-GaN. Additionally, the low Mg doping near the p-GaN/AlGaN interface, naturally formed in epitaxial growth, relaxes the precision required for t_R control to maintain charge balance. Under the optimal t_R, we demonstrate a 10 kV GaN E-mode HEMT with a specific on-resistance (R_ON,SP) of 69 mΩ cm², which is lower than the R_ON,SP of 10 kV SiC MOSFETs. We also test a 5 kV device under prolonged high-temperature reverse bias stress at 3 kV and 150 °C. The device shows minimal parametric shifts, manifesting electrical and thermal reliability of the underlying charge modulation. The findings offer valuable guidance for the design of multi-kilovolt GaN power HEMTs using industry-standard wafers.