E-mode AlGaN/GaN True-MOS, with high-k ZrO2 gate insulator

We report on fabrication of enhancement-mode True-MOS high electron mobility transistor (HEMT) with ZrO₂ gate dielectric. The GaN cap and AlGaN layers in the gate area are completely recessed by dry etching up to the GaN channel layer. The increase in channel resistance subsequent to the recess is compensated by adopting sub-micrometer gates and the negative V_th shift is mitigated by using a high-k dielectric. The maximum output current of 0.45 A/mm for a 0.5 μm gate length shows that the above concept can be promising for switching applications.