THz Oscillation in Doped-GaN Based Planar Gunn Diode with the T-shape Channel

In this study, the performance of a doped-GaN-based planar Gunn diode (PGD) with a T-shape channel is investigated through numerical simulations. The effects of the vertical electric field and the surface geometry are considered simultaneously through three-dimensional (3D) simulations. For comparison, 2D simulations are performed on the top view of the 3D structure. The dependence of the velocity on the electric field and doping density is calibrated. Differences in I-V characteristics and oscillation behaviour between 2D and 3D simulations are demonstrated. A high-frequency mode has been observed in 3D simulations at high voltage due to the formation of multiple dipole domains, which are not well represented in 2D simulations. The critical voltage of the low-frequency mode to high-frequency mode transition is found to reduce with the active layer thickness. With a 150 nm thick active layer, the oscillation frequency at 30 V estimated by the 3D simulation is higher than 600 GHz.