Epitaxial $Bi∕GaAs$ diodes via electrodeposition

Epitaxial $Bi∕GaAs$ diodes have been formed by electrodeposition from bismuth nitrate and ammonium sulfate $((NH4)2SO4)$ aqueous solutions. Bi grows (0001) oriented on both GaAs $(111)B$ and (001) substrates while it tilts 16° to a $(011̱8)$ surface orientation for (011) GaAs. The metal orients in all cases with its ${112̱0}$ planes parallel the GaAs {110} planes. Diodes prepared on (001), $(111)B$⁠, and (011) wafers have current-voltage barrier heights $ΦBIV$ that vary from 0.74, to 0.76, to $0.83eV$ $(n=1.01–1.11)$⁠, respectively. These barrier heights straggle values from earlier reports for polycrystalline Bi deposited by ultrahigh vacuum techniques or electrodeposition. Barrier heights measured from high frequency, capacitance-voltage characteristics are higher than the $ΦBIV$ results, $0.06–1.5eV$⁠, as a function of the GaAs orientation, increasing in value in order of (011), (001), to $(111)B$⁠. This is explained by a combination of image force lowering and field emission corrections, and interface state/dipoles that are likely dependent on the GaAs orientation and on the degree of (0001) Bi alignment. These results are supported by cross-sectional transmission electron microscopy investigations indicating abrupt $Bi∕GaAs$ interfaces without evidence of a significant interfacial oxide or reacted layer.