X-Ray Photoemission Measurements of GaP, GaAs, InAs, and InSb

Abstract

X-ray-induced electron-emission measurements were used to determine the energy levels of core electrons in GaP, GaAs, InAs, and InSb. The investigated energy range extends from the bottom of the valence band to about 1400 eV below the Fermi level. Samples were cleaned by using argon-ion bombardment, and the gold $4f_{\frac{7}{2}}$ electron level was used to provide an energy reference level. Chemical shifts were determined by comparing the results with previously published experimental values for the pure elements. Several spin-orbit-splitting values were experimentally determined. Two maxima in the conduction-band density of states were located with respect to the bottom of the conduction band by comparing the photoemission data for the outermost core $d$ and $p$ electrons with transition energies measured by uv absorption, uv reflectivity, and electron-energy-loss experiments. One maximum is located between 0.8 and 1.4 eV above the bottom of the conduction band depending on the compound and the other is located between 3 and 4 eV.