ENHANCED CARRIER DENSITIES AND DEVICE PERFORMANCE IN PIEZOELECTRIC PSEUDOMORPHIC HIGH-ELECTRON MOBILITY TRANSISTOR STRUCTURES

The addition of a piezoelectric field in AlGaAs/InGaAs/GaAs HEMT structures is shown to lead to enhanced electron densities and hence improved device performance. Growth of a strained InxGa1-xAs layer is in [111] A direction causes a piezoelectric field to be built into the quantum well of a pseudomorphic HEMT, which opposes the electric field due to charge transfer and hence lowers the confinement energy. This leads to carrier densities 50% larger than in equivalent [100] structures, with the wave function also spaced further away from the dopant impurities and the well interfaces. We expect these factors to give improved device performance.