AlAs/GaAs Superlattice Barrier Unipolar Diode Structure

摘要

GaAs capacitor structures employing a thin undoped layer of (Al, Ga)As as a dielectric have been described and successfully used as gates in field effect transistors with transconductors exceeding 200 mS/mm at 77K. To improve the interface and bulk properties of the barrier, an AlAs/GaAs superlattice was substituted for the (Al, Ga)As. The I-V characteristics measured for the superlattice barrier structures had greatly reduced currents and a much larger degree of rectification than could be explained by conventional thermionic emission theory. A new theoretical model describing phonon-assisted emission provides a very good qualitative fit to the measured data. With the aid of this model we also find dramatic evidence for believing the conduction band offset in the AlAs/GaAs system is approximately 60% of the difference in the direct bandgaps. (ERA citation 10:003072)