The present status of modulation-doped and insulated-gate field-effect transistors in III-V semiconductors

A review of recent and current work on modulation-doped and insulated-gate field-effect transistors is presented. Deep depletion-mode GaAs IGFETs have achieved satisfactory microwave performance, while inversion-mode devices are not feasible at present. Other materials such as InP and InGaAsP have advantages for inversion-mode IGFETs. High electron mobility transistors (HEMT) have realized field-effect control of the high mobility electrons in modulation-doped GaAs/n-Alsub(x)Gasub(1-x)As single heterojunction structures. Mobility variation with carrier concentration and undoped Alsub(x)Gasub(1-x)As spacer thickness is briefly discussed. Logic performance obtained with enhancement-mode HEMTs is also presented. (orig.)