Rode's iterative calculation of surface optical phonon scattering limited electron mobility in N-polar GaN devices

N-polar GaN channel mobility is important for high frequency device applications. Here, we report theoretical calculations on the surface optical (SO) phonon scattering rate of two-dimensional electron gas (2DEG) in N-polar GaN quantum well channels with high-k dielectrics. Rode's iterative calculation is used to predict the scattering rate and mobility. Coupling of the GaN plasmon modes with the SO modes is taken into account and dynamic screening is employed under linear polarization response. The effect of SO phonons on 2DEG mobility was found to be small at >5nm channel thickness. However, the SO mobility in 3nm N-polar GaN channels with HfO₂ and ZrO₂ high-k dielectrics is low and limits the total mobility. The SO scattering for SiN dielectric on GaN was found to be negligible due to its high SO phonon energy. Using Al₂O₃, the SO phonon scattering does not affect mobility significantly only except the case when the channel is too thin with a low 2DEG density.