OBSERVATION OF CARRIER CONCENTRATION SATURATION EFFECT IN N-TYPE ALXGA1-XAS

In a series of Al0.3Ga0.7As epitaxial layers with Si doping concentrations varied from 1×1017 to 1.5×1018 cm-3, carrier concentration saturation effect was observed by Hall measurements. When Si doping concentration was increased, the carrier concentration tended to saturate. This is due to the negative U property of the donor DX center. The Fermi energy tends to be pinned at the free energy level of the DX center. This carrier concentration saturation effect should not be limit to only n-AlxGa1-xAs semiconductors. It is a general effect in n-type compound semiconductors when donor impurities induce negative U DX levels, and will have a great influence in designing optoelectronic and fast speed microelectronic devices.© 1995 American Institute of Physics.