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The core-level and valence band electronic structure of the n-GaAs (100) has been studied by synchrotron-based high-resolution photoelectron spectroscopy after irradiation by an Ar+ ion beam with energy Ei = 1500 eV and fluence Q = 1 × 1015 ions/cm2. Conversion of the conductivity type of the surface layer and formation of a p–n structure have been observed. The p-surface layer thickness (d ~ 5.0 nm) and band structure were experimentally determined from the Ga3d photoelectron spectrum by separation and analysis of the low intense n-type bulk contribution from deeper layers. A band diagram of the p–n junction formed on the n-GaAs surface by Ar+ ion bombardment was reconstructed. The p–n junction proved to be unexpectedly narrow compared to the extended tail of the implanted ion depth distribution.

A highly defective ~10-nm-thick layer was fabricated in a high vacuum by 2.5 keV Ar+ ion bombardment of the n-GaAs surface. Valence band photoelectron spectra showed a p-type conductivity of the layer arising due to the high concentration of mechanically created point defects (p-centers). J–V characteristics measured ex situ for the structure consisting of the irradiated p-layer on the n-type substrate revealed a diode effect. Analysis of the data attributes the effect to the formation of a specific p–n junction. Thereby, we demonstrated that Ar+ ion bombardment of the n-GaAs surface results in that a nanostructure with the p–n junction properties is formed. The p–n junction under consideration seems to deserve further study and possible application since it can be formed in high-vacuum clean conditions directly by exposure to a low-energy Ar+ ion beam without wet lithography.

Oxidation specific of the defected GaAs has been considered on the basis of elemental and chemical composition study of the oxide layer naturally emerged on the GaAs surface strongly irradiated by Ar+ ions with energy Ei = 3000 eV and fluence Q ~ 3 × 1015 cm–2. The diffusivity of elemental arsenic known to form an interface layer was shown to increase at room temperature by more than 35 orders of magnitude due to radiation defects and to amount to the value D ~ 1 × 10–17 cm2/s. Efficient room temperature diffusion results in total removal of elemental arsenic from oxide into the bulk, thus curing the damaged substrate.

The elemental and chemical compositions throughout the thickness of the GaAs native oxide layer slightly irradiated by Ar+ ions have been studied by synchrotron-based photoelectron spectroscopy at different photon energies enabling variation of probing depth. The presence of only two phases was observed: of the gallium oxide Ga2O3 and elementary arsenic Aso generated due to complete decay of arsenic oxides under the ion irradiation. Depth composition profiles were determined nondestructively. Despite inhomogeneous depth distribution, these profiles demonstrated domination (90 at %) of the dielectric Ga2O3 phase virtually throughout all the oxide thickness (~2 nm).

Poor dielectric properties of GaAs oxides are the drawback of the GaAs-based electronics preventing using these oxides as dielectric layers. The elemental and chemical compositions of the GaAs native oxide layer slightly irradiated by Ar+ ions with the fluence Q ~1 ∗ 1014 ions/cm2 have been studied by the synchrotron-based photoelectron spectroscopy. The effect of selective and total decay of arsenic oxides followed by diffusive escape of arsenic atoms from the oxide layer has been revealed. The effect results in three-fold Ga enrichment of the upper layer of the native oxide and in strong domination (~90 at%) of the Ga2O3 phase which is known to be a quite good dielectric with the bandgap width as wide as 4.8 eV. A band diagram was obtained for the native oxide nanolayer on the n-GaAs wafer. It has been shown that this natural nanostructure has a character of a p-n heterojunction.

Electronic structure and chemical composition of GaAs-based semiconductors are considered to be well characterized by photoelectron spectroscopy and other surface-sensitive methods. However, effect of ion irradiation on electron binding energies and band structure of semiconductors can drastically distort results of diagnostics. This effect was studied by synchrotron-based XPS applied to n-GaAs wafer after 1250 eV - Ar+ ion exposure with fluence Q ~ 1 × 1015 ions/cm2 which is typical for preparation of atomically clean surfaces. Mechanical action of ions was shown to change the n-GaAs electron binding energies by the value of the bandgap width due to creation of defect states, and conversion of the conductivity type from n to p. The Ga3d and As3d core-level binding energies for p-GaAs and n-GaAs were measured in one experiment on the p-n plane structure formed due to irradiation: EB(p/n) = 19.3/20.4 eV and EB(p/n) = 41.3/42.4 eV. The p-layer nanothickness was determined and the band diagram of the p-n GaAs structure was constructed. The revealed effect may be comparable with core-level chemical shifts and should be taken into account to avoid mistakes in the XPS chemical composition diagnostic of GaAs-based semiconductors.

The thickness, elemental and chemical compositions of the native oxide naturally formed on a perfect GaAs(1 0 0) crystal grown by MBE have been studied by Auger electron spectroscopy (AES) and electron energy-loss spectroscopy (EELS) to specify the oxidation mechanism and to confirm or reject the questionable presence of elemental arsenic in the natural oxide. Elemental arsenic (Aso) arising in the oxidation process due to reduction of As2O3 by the GaAs substrate was revealed at the Auger energy of 1225.8 eV and shown to reach ~16 at% of the oxide whose thickness was determined to be ~4 nm. Aso was shown by EELS to form a segregate with the plasmon energy of 18.1 eV. Room temperature oxygen diffusivity through the finally formed oxide layer was estimated to be low enough (D