Impact of geometric dimensions on the behavior of GaN MIS-HEMT fabricated on patterned sapphire substrate
In this paper, an AlGaN/GaN based MIS-HEMT using Al2O3 dielectric as gate insulator was fabricated. We adopted the patterned sapphire as the substrate (PSS) of high-quality AlGaN GaN epitaxial layers. We also studied the influence of different gate-drain space (L<sub>gd</sub>) on breakdown voltage (V<sub>BD</sub>) and on-state resistance (R<sub>on</sub>) of GaN HEMT fabricated on patterned sapphire substrate. A breakdown voltage of 105 V was obtained with the L<sub>gd</sub> of 2 μm and gate width of 32 μm. The specific on resistance was 4.7 Ω·mm when L<sub>gd</sub> equals 0.5 μm. Meanwhile, it is found that the devices fabricated on the wet-etched pyramidal patterned sapphire substrate GaN exhibit better drive current stability than that of the devices on the conventional GaN-on-Sapphire substrate.