Breakdown voltage enhancement in GaN channel and AlGaN channel HEMTs using large gate metal height

A large gate metal height technique is proposed to enhance breakdown voltage in GaN channel and AlGaN channel high-electron-mobility-transistors (HEMTs). For GaN channel HEMTs with gate-drain spacing L_GD=2.5 μm, the breakdown voltage V_BR increases from 518 V to 582 V by increasing gate metal height h from 0.2 μm to 0.4 μm. For GaN channel HEMTs with L_GD=7 μm, V_BR increases from 953 V to 1310 V by increasing h from 0.8 μm to 1.6 μm. The breakdown voltage enhancement results from the increase of the gate sidewall capacitance and depletion region extension. For Al_0.4Ga_0.6N channel HEMT with L_GD=7 μm, V_BR increases from 1535 V to 1763 V by increasing h from 0.8 μm to 1.6 μm, resulting in a high average breakdown electric field of 2.51 MV/cm. Simulation and analysis indicate that the high gate metal height is an effective method to enhance breakdown voltage in GaN-based HEMTs, and this method can be utilized in all the lateral semiconductor devices.