heterojunction field effect transistor (HFET)
Heterojunction field-effect transistors (HFET) have comparable properties to MESFETs. They are used in microwave technology and in high-speed digital circuits.
HFETs are characterized by the ability to increase electron mobility near the interface between two semiconductors by using different band gaps. In heterojunction field-effect transistors, the channel is formed by the bandgap than by the electron affinity. Due to the extremely short-time rates of change, HFETs are used for switches and low- noise RF amplifiers. As semiconductor material, HFETs use aluminum gallium arsenide( AlGaAs) and gallium arsenide( GaAs).