摘要: The concepts, technology and the present experimental limits of performance of heterojunction modulation doped field effect transistors are covered. Both lattice-matched and strained, pseudomorphic quantum well channels on GaAs su... 展开 The concepts, technology and the present experimental limits of performance of heterojunction modulation doped field effect transistors are covered. Both lattice-matched and strained, pseudomorphic quantum well channels on GaAs substrates, as well as lattice-matched quantum well channels on InP substrates are included. Power gain frequency limits to 450 GHz, and noise figures as low as .8-.9 db at 60 GHz are presented for 300K operation of the latter devices. Microwave and millimeter wave field effect transistors have reached impressive performance levels by the use of heterojunctions. In these structures, a lower band-gap layer holds the electrons, while a higher band-gap layer is doped with donor atoms. As well as lattice-matched combinations on GaAs and InP substrates, thin strained layers have been used to hold the electrons. Very short gates have been realized using electron-beam lithography. This presentation covers the materials used, the fabrication methods, the materials and device assessment methods, and the present performance limits. 收起