High Mobility Inverted Modulation Doped Field-Effect Transistors
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
A technique is described whereby inverted heterojunction Modulation doped field-effect transistor (MODFET) semiconductor devices with high mobility are grown, utilizing reflection high energy electron diffraction (RHEED) oscillations. Utilizing molecular beam epitaxy (MBE) tech- niques, devices with mobilities as high as 500K cm2/volt-sec measured at 4K have been fabricated. Inverted heterojunction devices, where the alloy containing doping (mostly AlGaAs) is grown first and the pure binary (mostly GaAs) is grown on the top, have been regarded as inferior since the mobilities were lower than those measured in normal heterojunctions (layers grown in the opposite sequence). Typical 77 K mobilities have measured 20 - 40K cm2/volt-sec for inverted structures and 120 - 180K cm2/volt-sec for normal structures.