Evolution ofGaAs1−xNxconduction states and giantAu/GaAs1−xNxSchottky barrier reduction studied by ballistic electron emission spectroscopy

Abstract

The evolution of ${\mathrm{GaAs}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ band structure at low nitrogen concentrations (up to $x=0.021)$ is studied by ballistic electron emission microscopy (BEEM) spectra of ${\mathrm{A}\mathrm{u}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ heterostructures. Two peaks observed in the second derivative BEEM spectra are identified with the contribution from the \ensuremath{\Gamma}- and L-like bands of ${\mathrm{GaAs}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}.$ As the nitrogen concentration increases, the energetic separation between these peaks increases, with a relative decrease of the L-like band contribution to the BEEM current. In addition, we found a strong decrease of the ${\mathrm{A}\mathrm{u}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ Schottky barrier with the nitrogen incorporation, from $\ensuremath{\sim}0.92 \mathrm{eV}$ at $x=0$ down to $\ensuremath{\sim}0.55 \mathrm{eV}$ at $x=0.021.$ The observed Schottky barrier reduction approximates the ${\mathrm{GaAs}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ band-gap reduction.