Measurement of the valence-band offset at the epitaxial MgO-GaAs(001) heterojunction by x-ray photoelectron spectroscopy

Abstract

The electronic band structure at the interface of the MgO-GaAs(001) tunnel contact has been experimentally studied. X-ray photoelectron spectroscopy has been used to measure the valence-band offset at the MgO-GaAs(001) heterojunction interface. The valence-band offset ΔEV is determined to be 4.2±0.1eV. As a consequence, a nested “type-I” band alignment with a conduction-band offset of ΔEC=2.2±0.1eV is found. The accurate determination of the valence and conduction band offsets is important for the fundamental understanding of the tunnel spin injection in GaAs.

Fabrication of high-quality ZnCdO epilayers and ZnO/ZnCdO heterojunction on sapphire substrates by pulsed laser deposition

“…The VBM position relative to the surface Fermi level are obtained by linear extrapolation of the leading edge to the extended base line of the VB spectra with an energy reference of E ZnO VBM = 0 eV. This linear method has already been widely used to determine the VBM of semiconductors with an accuracy of about ±0.05 eV [35,36]. In addition, the Zn 2p 3/2 CL spectra were fitted to a Voigt (mixed Lorentzian-Gaussian) curve using a Shirley background and the binding energy for the CL peaks are taken as the energy corresponding to the maximum intensity.…”

Band structure of the epitaxial Fe∕MgO∕GaAs(001) tunnel junction studied by x-ray and ultraviolet photoelectron spectroscopies

“…MgO − E VBM MgO ͒ has already been carefully determined to be 18.06 eV, 6 the SBH ⌽ BS can be deduced from the measurement of ⌬E FC . Figure 2 shows XPS spectra of O2s and Ga3d core levels and Fe FLs for different samples, respectively, 3 nm MgO / GaAs before Fe deposition, 3 nm MgO / GaAs after 2 nm Fe deposition, and 2 nm Fe deposited on an UHV-cleaved MgO monocrystal.…”

“…In our previous work, we precisely determined by XPS a valence band offset ͑VBO͒ ⌬E V = 4.2± 0.1 eV and a conduction band offset ⌬E C = 2.2± 0.1 eV at the MgO / GaAs͑001͒ interface. 6 As XPS measurements are slightly averaged in depth, band bending in the MgO layer could induce a systematic error in our measurements. To check this point, we have grown MgO with different thicknesses ͑2, 3, and 4 nm͒ on GaAs.…”

“…Details about the preparation of the MgO / GaAs͑001͒ samples can be found elsewhere. 6 Briefly, 3 nm thick MgO͑001͒ layers were grown on Si n-doped ͑4 ϫ 10 16 cm −3 ͒ GaAs As͑2 ϫ 4͒ surface at RT by evaporation of high purity MgO powder. After MgO growth, the samples were annealed under ultrahigh vacuum ͑UHV͒ at 600°C for 20 min.…”

Band alignment of InN∕GaAs heterojunction determined by x-ray photoelectron spectroscopy

“…Moreover the strain-induced piezoelectric field effect is neglected in our experiment, as in the case of measuring the band offset by XPS by others. 9,10 Since the overlayer of the heterojunction is as thin as ϳ3 nm, the InN/ GaAs sample can be approximately treated as consisting of surface and interface. So, the band bending effect can be neglected in this experiment, as was the measurement of the band offset of the InN/ AlN heterojunction by others.…”