The invention relates to a high-
linearity depletion type high-
electron-mobility
transistor and a preparation method thereof. The high-
electron-mobility
transistor comprises a substrate, a nucleating layer, a buffer layer, a channel layer, an intermediate layer, a
barrier layer, a cap layer, a source
electrode, a drain
electrode, a
passivation layer, a
gate dielectric layer, a plurality of first gate
metal and a plurality of second gate
metal. The substrate, the nucleating layer, the buffer layer, the channel layer, the intermediate layer, the
barrier layer and the cap layer are stacked in sequence; the source
electrode and the drain electrode are respectively located at two ends of the cap layer; the
passivation layer is located on the cap layer between the source electrode and the drain electrode, and a groove extending to the cap layer is formed in the gate region; the
gate dielectric layer covers the
passivation layer and the surface of the groove; a plurality of first gate metals are distributed in the groove at intervals along the gate width direction; the second gate
metal covers the plurality of first gate metals and the
gate dielectric layer between the first gate metals; the
work function of the first gate metal and the
work function of the second gate metal are different. The
transistor reduces the
nonlinear distortion of the output
signal.