Carrier concentration saturation in n type AlxGa1-xAs

Abstract

Due to the negative U property of donor DX center, the Fermi energy tends to be pinned to the DX center free energy level when the Si doping concentration is increased. Correspondingly, the carrier concentration tends to saturate. It is a general property in n-type compound semiconductors when donor impurities induce negative U DX levels in the energy gap. In this work, in a series of Al0.3Ga0.7As epitaxial layers with different Si doping concentrations varied from 1×1017cm-3 to 1.5×1018cm-3, carrier concentration saturation effect was observed by Hall measurements. This effect will have great influence in designing optoelectronic and fast microelectronic devices.