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•The MBE GaAs natural oxide is a self-organized layered structure “As2O3/oxide core/Aso”.•The Aso monolayer exists near the “oxide/ MBE GaAs-substrate” interface.•The GaAs oxide core ...is enriched in Ga due to the Aso room temperature out-diffusion.•The oxygen diffusivity through the GaAs oxide layer does not exceed D ~ 1 *10−21 m2/s.•The Auger and plasmon energies of the arsenic monolayer are EA = 1225.8 eV, ħω = 18.1 eV.
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 < 10−21 m2/s) to explain retention of the Aso in the deepest oxide layers where it cannot oxidize again or diffuse away. The studied natural oxide was shown to have a layered nanostructure consisting of a cap As2O3 layer (~1 nm), a core oxide layer containing a Ga2O3/As2O3 mixture (~2 nm) enriched in Ga by a factor of 1.5, and a deep interface layer of elemental arsenic (~1 nm).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Detailed information on GaAs oxide properties is important for solving the problem of passivating and dielectric layers in the GaAs-based electronics. The elemental and chemical compositions of the ...native oxide layer grown on the atomically clean surface of an
n
-GaAs (100) wafer etched by Ar
+
ions have been studied by synchrotron-based photoelectron spectroscopy. It has been revealed that the oxide layer is essentially enriched in the Ga
2
O
3
phase which is known to be a quite good dielectric as compared to As
2
O
3
. The gallium to arsenic ratio reaches the value as high as Ga/As = 1.5 in the course of oxidation. The Ga-enrichment occurs supposedly due to diffusion away of As released in preferential oxidation of Ga atoms. A band diagram was constructed for the native oxide nanolayer on the
n
-GaAs wafer. It has been shown that this natural nanostructure has features of a
p–n
heterojunction.
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—
A number of mechanisms of the diffusion of arsenic atoms including the radiation- stimulated vacancy, interstitial, and mixed (Frank—Turnbull mechanism) types are considered to explain the earlier ...discovered ion-stimulated transformation of a layer of native GaAs oxide into a layer of Ga
2
O
3
at room temperature. An estimate of the diffusion coefficients and lengths makes it possible to conclude that the interstitial diffusion mechanism dominates at a fluence
Q
< 10
15
cm
–2
. It is found that at room temperature, when the interstitial mechanism is implemented, the diffusion coefficient (
D
As
~ 1.3 × 10
–16
cm
2
/s) and the diffusion length (
L
> 9 nm) are sufficient to remove elemental arsenic formed under the action of argon ions from a layer of native oxide with a thickness of 2.0–2.5 nm in 10 minutes. However, the contribution of the vacancy mechanism increases with increasing irradiation dose due to an increase in the concentration of vacancies. In this case, the diffusion mechanism becomes mixed. At a fluence of
Q
> 10
15
cm
–2
, the vacancy mechanism provides a diffusion coefficient (
D
As
~ 0.7 × 10
–17
cm
2
/s) and diffusion length (
L
> 2.5 nm) also sufficient to remove elemental arsenic from the oxide layer within 10–20 min. It is shown that the diffusion of arsenic can be significant in the processes of chemical modification of GaAs oxides even at room temperature.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
4.
Features of Oxidation of Ar+-Ion-Irradiated GaAs Solonitsyna, A. P.; Makarevskaya, E. A.; Novikov, D. A. ...
Surface investigation, x-ray, synchrotron and neutron techniques,
10/2022, Volume:
16, Issue:
5
Journal Article
Peer reviewed
The features of oxidation of the surface of GaAs irradiated by low-energy Ar
+
ions is considered based on elemental and chemical-composition analyses, calculations of the concentration profiles for ...radiation-induced defects, and estimations of radiation-enhanced diffusivities and diffusion lengths. The native oxide layer is revealed to be highly enriched with Ga (by a factor of 1.5) due to the radiation-enhanced diffusion of elemental arsenic through vacancy defects even at room temperature. Elemental arsenic emerging at the interface with the oxide layer moves to a deeper radiation-damaged layer and fills vacancies there. At irradiation doses of
Q
> 3 × 10
14
cm
–2
, which are sufficient for removal of the oxide layer with 3-keV Ar
+
ions, elemental arsenic leaves the oxide layer within one hour, and the diffusion length reaches the thickness of the radiation-damaged layer within one day. The total number of vacancies in the radiation-damaged layer is enough to absorb all elemental arsenic formed during oxidation. The considered radiation-enhanced diffusion can be used to remove elemental arsenic, which is known to form nonradiative recombination centers quenching the luminescence of the underlying bulk layer, from the oxide layer.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
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•A selective ion-induced transformation of As2O3 into elemental As in GaAs oxide.•Threefold ion-induced enrichment in Ga in the GaAs oxide layer ~1 nm thick.•Ion-induced transformation of GaAs oxide into Ga2O3 dielectric.•A band diagram of the native oxide nanolayer on the n-GaAs wafer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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
E
i
= 3000 eV and fluence
Q
~ 3 × 10
15
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
cm
2
/s. Efficient room temperature diffusion results in total removal of elemental arsenic from oxide into the bulk, thus curing the damaged substrate.
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Particle trajectories are calculated to study the rainbow scattering and the focusing of Ar atoms on the Al(111) and Ag(111) crystal surfaces and Ne, Ar, and Kr atoms on the Al(001) crystal surface. ...The rainbow-scattering-induced features in spectra are used to determine the thermal vibration amplitudes of atoms for the Al(111) and Ag(111) targets. These data agree with the data of independent measurements. The dependence of the position of a rainbow peak on the initial energy of atoms is used to find the atom–surface interaction potentials in the energy range of 0.3–70 eV for the case Ar–Ag and 3–45 eV for other cases. The values and the functional dependences of the potentials on the internuclear distance differ strongly from the well-known pair potential models. This difference is associated with the interaction of a projectile atom with the conduction electrons in a metal.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
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•A selective ion-induced transformation of As2O3 into elemental As in GaAs oxide.•Threefold ion-induced enrichment in Ga in the GaAs oxide layer ~1 nm thick.•Ion-induced transformation of GaAs oxide into Ga2O3 dielectric.•A band diagram of the native oxide nanolayer on the n-GaAs wafer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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 Ga
2
O
3
and elementary arsenic As
o
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 Ga
2
O
3
phase virtually throughout all the oxide thickness (~2 nm).
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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
E
i
= 1500 eV and fluence
Q
= 1 × 10
15
ions/cm
2
. 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.
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