In situ, near-ideal epitaxial Al/Al_xGa_1-xAs Schottky barriers formed by molecular beam epitaxy

The Schottky barrier height of in situ epitaxial aluminum on Al _xGa_1-xAs was measured as a function of aluminum mole fraction from x=0 to x=1, using I/V, C/V and activation energy plots of current-voltage dependence on temperature. The excellent electrical properties of the molecular beam epitaxy grown AlGaAs layers, with residual deep levels concentrations of less than 10¹⁴ cm^-3 combined with the in situ deposition of single-crystal epitaxial aluminum resulted in extremely high quality Schottky diodes from x=0 (GaAs) to x=1 (AlAs) with accurately exponential current-voltage characteristics over up to 10 decades and with ideality factors less than 1.03. Both the C^-2-V and activation energy plots were linear and yielded barrier heights in very good agreement with the I/V ones. The near-ideal characteristics of these diodes were compared with several models of Schottky barrier formation and the dependence of the Schottky barrier height on the aluminum mole fraction was found to agree with the anion vacancy model within 10-20 meV, with a maximum deviation of 46 meV.