EFFECT OF OXYGEN INCORPORATION AT ALGAAS GAAS INTERFACES ON THE ELECTRICAL-PROPERTIES OF 2-DIMENSIONAL ELECTRON-GAS/

We have investigated the carrier concentration and mobility of the two -dimensional electron gas (2DEG) in AlGaAs/GaAs selectively doped hete rojunction structures that involve oxygen impurities at the heterointe rfaces, The oxygen impurities were incorporated during growth interrup tion of molecular beam epitaxy at the interfaces for several tens of m inutes. It is shown that the carrier concentration of the 2DEG does no t change for the areal density of the oxygen impurity up to 6X10(11) c m(-2), but it decreases drastically when the oxygen density exceeds 3X 10(12) cm(-2). In contrast, the decrease of the mobility is observable for a much smaller oxygen density of the order of 10(10) cm(-2). We s how that these influences are well explained by the formation of charg ed states at the interface. (C) 1997 American Institute of Physics.