Backgating studies in In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As modulation-doped field-effect transistors

A study is presented of the backgating effects in normal and inverted modulation-doped field-effect transistors (MODFETs) grown by molecular-beam epitaxy and their dependence on material properties and device geometry. The experiments were performed on devices with 2- mu m gate lengths. The effects of both positive and negative (with respect to the source of the experimental devices) voltages applied to both ohmic and Schottky side contacts were investigated. The inverted MODFET structures, which have a very-high-resistance InAlAs 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.<
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