Influence of n-GaAs/i-AlGaAs heterostructure interfaces on the electrical properties of the n-GaAs channel layer

The electrical properties of the n-type GaAs channel layer on various buffer layers of GaAs and AlGaAs were investigated,, using epitaxial wafer samples grown by metal-organic vapor phase epitaxy (MOVPE) with very low contamination at the epitaxial/substrate interface. The n-GaAs/i-AlGaAs interface was found to enlarge the depletion layer and to reduce the mobility near the interface. This unexpected effect was explained by a model which took into consideration the compensation of the carbon acceptor by the oxygen deep donor in AlGaAs. By decreasing the oxygen concentration, the properties complied well with the basic theory, Poisson's equation and continuity equations. These results are very useful in the design of an epitaxial wafer for a device with a GaAs channel and heterostructural buffer laver. (C) 1997 Elsevier Science S.A.