The invention relates to an enhanced GaN-based MIS-HEMT device and a preparation method thereof. In the MIS-HEMT device, a concave AlGaN
barrier layer is arranged on the basis of a thin AlGaN barrierlayer, so that the channel mobility is improved, and the
on resistance is improved. On the basis, an
electron beam
evaporation (EBE) method is adopted to grow a
mask layer and is combined with an SAGmethod, compared with a PECVD
mask used in a conventional process, the adoption of the EBE for growing the
mask completely eliminates
plasma damage in the mask technology, and damage-free
crystal lattices are reserved for a thin AlGaN / GaN
heterojunction. Meanwhile, the Al component of the AlGaN thin
barrier layer is different from the Al component of the concave AlGaN
barrier layer, and the
threshold voltage and the channel
electron mobility are further improved. In addition, a
gate dielectric layer in the device is formed by stacking three
oxide materials with different
dielectric constants,the thickness of the
dielectric layer is increased to ensure a certain
threshold voltage, and the
gate capacitance is increased by means of increasing the
dielectric constant, so that the
transconductance value is prevented from being too low.