AlGaN/GaN self-aligned MODFET with metal oxide gate for millimeter wave application

As promising candidates for future microwave power devices, GaN-based high-electron mobility transistors (HEMTs) have attracted much research interest. An investigation of the operation of AlGaN/GaN n type self-aligned MOSFET with modulation doped GaN channels is presented. Liquid phase deposited (LPD) SiO2 is used as the insulating material. An analytical model based on modified charge control equations is developed. The investigated critical parameters of the proposed device are the maximum drain current (IDmax), the threshold voltage (Vth), the peak DC trans-conductance (gm), break down voltage (Vbr) and unity current gain cut-off frequency (fT). The typical DC characteristics for a gate length of 1 μm with 100 μm gate width are following: Imax=800 mA/mm, Vbreak-down=50 V, gm_extrinsic=200 mS/mm, Vpinchoff=−10 V. The analysis and simulation results on the transport characteristics of the MOS gate MODFET structure is compared with the previously measured experimental data. The calculated values of fT (20–130 GHz) suggest that the operation of the proposed device effectively, has sufficiently high current gain cutoff frequencies over a wide range of drain voltage, which is essential for high-power performance at microwave frequencies. The proposed device offers lower on-state resistance. The results so obtained are in close agreement with the experimental data.