[MoC4] GaN HEMTs for Power (I)

5:00 PM - 5:15 PM JST(8:00 AM - 8:15 AM UTC)

[MoC4-03] Development of N-polar GaN HEMTs with p-GaN Gates

〇Robert Hamwey¹, Tanmay Chavan¹, Boyu Wang¹, Nirupam Hatui¹, Stacia Keller¹, Umesh K. Mishra¹ (1. University of California (USA))

N-polar GaN HEMTs exhibit reversed polarization fields relative to extensively studied and commercially mature Ga-polar HEMTs due to the noncentrosymmetric nature of wurtzite GaN. The N-polar polarization field in HEMTs provides a natural back barrier for two-dimensional electron gas (2DEG) confinement, enables reduced 2DEG ohmic contact resistance, and allows for aggressive gate-to-channel scaling while maintaining a high 2DEG density. Although Mg-doped p-GaN gates are widely used in Ga-polar GaN power HEMTs, their integration in N-polar heterostructures remains unexplored. In this work, we establish an epitaxial process space for incorporating p-GaN gates in N-polar HEMTs. High-quality 2DEG properties are obtained by limiting Mg back-diffusion from the p-GaN gate into a 30 nm GaN channel.
We demonstrate that 2DEG preservation can be achieved by tuning p-GaN growth temperature and inserting an Al(Ga)N spacer between the N-polar HEMT channel and the p-GaN gate. 2DEG quality is evaluated by Hall and transfer length method (TLM) measurements and p-GaN gate control is confirmed using capacitance–voltage (C-V) structures. 2DEG transport characteristics are compared to Mg SIMS profiles to determine the impact of Mg back-diffusion.
Lastly, we showcase preliminary characteristics (DC output and transfer characteristics) of the first reported N-polar GaN HEMT with a p-GaN gate.