1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor

In this paper, we present a 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor (DH HEMT) with a gate-drain spacing L_GD=18.8 μm. Compared with the regular DH HEMT, our circular structure has a high average breakdown electric-field strength that increases from 0.42 MV/cm to 0.96 MV/cm. The power figure of merit V_BR²/R_ON for the circular HEMT is as high as 1.03×10⁹ V₂·Ω^-1·cm^-2. The divergence of electric field lines at the gate edge and no edge effect account for the breakdown enhancement capability of the circular structure. Experiments and analysis indicate that the circular structure is an effective method to modulate the electric field.