Effect of Device Scaling on Electron Mobility in Nanoscale GaN HEMTs with Polarization Charge Modulation

We have experimentally investigated the impact of vertical and lateral scaling on low-field electron mobility (µ) in InAlN/GaN high-electron-mobility transistors (HEMTs). It is found that µ reduces as InAlN barrier (T_B) and gate length (L_G) scale down but increases with the scaled source-drain distance (L_SD). Polarization Coulomb Field (PCF) scattering is believed to account for the scaling-dependent electron mobility characteristic. The polarization charge distribution is modulated with the vertical and lateral scaling, resulting in the changes in µ limited by PCF scattering. The mobility characteristic shows that PCF scattering should be considered when devices scale down, which is significant for the device design and performance improvement for RF applications.