Stability analysis of multi-finger GaN FET cells for high power MMIC design

FET cells used in high power amplifier designs often require large gate-to-gate spacing (pitch) in order to manage the heating due to the large power dissipation inside the cell and keep the channel temperature below the critical level. However, as the technology is advanced to achieve FETs with higher ft and fmax frequencies, FET cell with large gate-to-gate pitch can become prone to internal oscillation at high frequencies. The nature of this oscillation is studied in this manuscript, and methods for stabilizing the FET cells are presented.