A HEMT has an InAlAs layer (202), an InGaAs layer (203), a multiple
-doped InAlAs layer (204) composed of n-type doped layers (204a)
and undoped layers (204b) which are alternately stacked, an InP layer
(205), a Schottky gate electrode (210), a source electrode (209a),
and a drain electrode (209b) on an InP substrate (201). When
a current flows in a region (channel region) of the InGaAs layer (203) adjacent
the interface between the InGaAs layer (203) and the multiple -doped
InAlAs layer (204), a breakdown voltage in the OFF state can be increased,
while resistance to the movement of carriers passing through the multiple -doped
InAlAs layer (204) as a carrier supplying layer is reduced.
