Backgating Studies in In(0.53)Ga(0.47)As/In(0.52)Al(0.48)As Modulation-Doped Field-Effect Transistors

摘要

A systematic study of the backgating effects in normal and inverted modulation-doped field-effect transistors (MODFET's) grown by molecular-beam epitaxy and its dependence on materials properties and device geometry has been made. The experiments have been performed on devices wth 2-micrometer gate lengths. The effects of both positive and negative (with respect to the source of the experimental device) voltages applied to both ohmic and Schottky side contacts have been investigated. The inverted MODFET structures, which have a very high-resistive indium aluminum arsenide buffer layer, showed negligible backgating characteristics up to side-contact voltages as high as 50 V. The normal structures, on the other hand, were very sensitive to the side-contact voltages with essentially a zero threshold voltage. This observation, together with the large measured sidegate currents, indicates a large conductivity and the absence of traps in the indium gallium arsenide layer. Relevant comparisons have been made with gallium arsenide/aluminum gallium arsenide MODFET's, also grown by MBE. Reprints.