Structure of heterojunction field effect transistor and a fabrication method thereof

Abstract

An improved structure of heterojunction field effect transistor (HFET) and a fabrication method thereof are disclosed. The improved HFET structure comprises sequentially a substrate, a channel layer, a spacing layer, a carrier supply layer, a Schottky layer, a Schottky capping layer formed by a higher energy gap material, a tunneling layer formed by a lower energy gap material, a first etching stop layer, and a first n type doped layer. The fabrication method is a multiple selective etching process, which comprises steps of: etching the n type doped layer by using a first etching process to form a first indentation; etching first etching stop layer by using a second etching process to form a second indentation located under the first indentation; etching the tunneling layer by using a third etching process to form a third indentation located under the second indentation, wherein the said first, second and third indentations form a single gate groove, in which the gate electrode can form a Schottky contact with the Schottky capping layer that is made of a higher energy gap material.