Influence of MBE growth and rapid thermal annealing conditions on the electrical properties of normal and inverted AlGaAs/InGaAs pseudomorphic HEMT structures

High-quality normal and inverted AlGaAs/InGaAs HEMT (high-electron-mobility transistor) structures have been grown on GaAs substrates by MBE (molecular-beam epitaxy), and the influence of rapid thermal annealing on electrical conduction in the two-dimensional electron gas (2-DEG) has been studied. Both close-contact and enhanced arsenic overpressure annealing have been examined. It has been found that inverted pseudomorphic HEMTs exhibit superior electrical properties with significantly higher sheet carrier concentrations than corresponding normal HEMTs. The unusual degree of thermal stability exhibited by these structures underlines the importance of maintaining high column V overpressures during high-temperature processing of HEMTs and demonstrates the ability of these devices to withstand annealing conditions typically used to activate implants in a self-aligned IC technology.<
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