NORMALLY-OFF HETEROJUNCTION FIELD EFFECT TRANSISTOR

摘要

A normally-off HFET includes, in a sequentially layered manner: an undoped AlwGa1-wN layer (11) having a thickness t1; an undoped AlxGa1-xN layer (11b) having a thickness t2 and an updoped GaN channel layer (11a) having a thickness tch; a source electrode (21) and a drain electrode (22) electrically connected to the channel layer and formed so as to be separated from each other; an undoped AlyGa1-yN layer (12) having a thickness t3 formed on the channel layer between the source electrode and the drain electrode; an AlzGa1-zN layer (13) having a thickness t4 formed as a mesa on a partial region of the AlyGa1-yN layer between the source electrode and the drain electrode; and a Schottky barrier gate electrode (23) formed on the AlzGa1-zN layer; and satisfies the conditions y>x>w>z, t1>t4>t3, and 2wtch/(x-w)>t2>1nm.