TUNABLE SCHOTTKY BARRIERS AND THE NATURE OF SI INTERFACE LAYERS IN ALGAAS(001) DIODES/

Silicon layers grown by molecular beam epitaxy in the interface region of Al/n-GaAs(001) Schottky diodes have been shown to tune the Schottk y barrier height in the 0.3-1.1 eV range, provided that high enough ex cess fluxes of As or Al ate employed during Si deposition. We studied the incorporation of As and Al in the interface layer for Si growth te mperatures of 300 and 400 degrees C, and for interlayer thicknesses in the 10-150 Angstrom range. Following deposition under an excess As fl ux we found an As atomic concentration c(As)=0.4-0.5 at 300 degrees C and c(As)=0.2 at 400 degrees C. The excess Al flux yielded an Al atomi c concentration c(Al)=0.7-0.8 at 300 degrees C, and c(Al)=0.6-0.7 at 4 00 degrees C. Correspondingly, the lattice structure of the interlayer s appears dramatically different from that of Si. We conclude that the 10-100 Angstrom interface layers used by some authors to change the b arrier height bear little resemblance to degenerate built Si, so that several of the mechanisms proposed to explain Schottky barrier tuning should be reevaluated. (C) 1996 American Vacuum Society.