Analyses of surface preparation, anodic oxidation, and epitaxial layers of GaAs using nuclear backscattering

Strømsheim, J. P.; Olsen, T.; Ruzicka, D. J.

doi:10.1002/pssa.2210390118

Cited by 9 publications

(8 citation statements)

References 12 publications

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“…They also showed that the first metal overlayer is important in determining the interface behaviour and emphasized the need of a microscopic theory of chemical bonding to clarify the suggestion that the metal forms covalent bonds with the semiconductor surface, giving rise to the observed Fermi level pinning by the metal-induced states. Photoeinission studies [53] strikingly show that the Fermi level already stabilizes at submonolayer amounts of Au near the position observed a t relatively thick coverages or for bulk Au on cleaved surfaces Ellipsometry [55], RHEED [56], backscattering measurements [57], and AES-SIMS depth profiling [58] have shown the existence of such an interface layer which differs in chemical composition from the bulk and froin the oxide overlayer. Depending on the stoichionietric deviations [58] the interface layer probably exhibits a large number of atomic defects.…”

Section: Discussionmentioning

confidence: 99%

Character of surface states at GaAs surfaces

Kreutz

1979

Phys. Stat. Sol. (a)

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The analysis of field effect measurements and of thermally stimulated currents allows t o derive the general shape of the distribution of surface states for GaAs surfaces. The density of fast snrface states consists out of a continuous distribution with a minimum near the niiddle of the energygap as well as increasing tails towards the band edges. About the middle of the forbidden gap a peaking distribution is superposed to the continuous distribution. The response to physical and chemical influence allows to discriminate between intrinsic and extrinsic surface states. This distribution of surface states qualitatively yields a satisfactory description of the experimental results. Die Analyse von Messungen des Feldeffektes und [thermisch stimulierter Strome liefert dasGaAs-Oberflachen das Termspektrum der Oberfliichenzustande. Die Dichte der Oberfliichenzustande zeigt ein Minimum nahe der Mitte der verbotenen Zone und steigt zu den Bandkanteii an. Etwa in der Mitte der verbotenen Zone ist dem kontinukflichen Termspektrum eine Gruppe energetisch verteilter Oberflachenstande uberlagert. Die Anderungen der Termspektren gegenuber physikalischen und chemischen Einfldssen erlaubt, zwischen intrinsischen und extrinsischen Oberflachenzustanden zu unterscheiden. Das Termspektrum der Oberflachenzustande beschreib t qualitativ befriedigend die experimentellen Ergebnisse.

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Section: Discussionmentioning

confidence: 99%

Character of surface states at GaAs surfaces

Kreutz

1979

Phys. Stat. Sol. (a)

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“…Thus, we may tentatively conclude that the surface of the K2Cr2OT-grown oxide film is mainly a mixture of As205 -5 Ga~O3 and the As205 decomposed into As205 and As~O3 during ion sputtering (Eq. [7]). The finding that the elemental As peak at about 41.6 eV, which would appear in the sputtering of As203 (Eq.…”

Section: Resultsmentioning

confidence: 99%

“…From Eq. [1]- [7], one gets the corrected concentration ni,j as follows nGa(As),GaAs ---AGa(As),GaAs/C [8] nGa,Ga~O3 --AGa,Ga2oJC [9] nA~,A~208 = [AA~,A~O3 --A~o5{5S (O/As5 +) --5}/{5…”

Section: Resultsmentioning

confidence: 99%

“…The depth profiles of the anodic oxide on GaAs have been studied by using techniques such as AES (1, 2), XPS (3,4), 1SS (5), nuclear backscattering (6,7), and radioactive tracers (8). The data of the As/Ga ratio in the anodic oxide showed that the oxide displayed three distinct layers; these are the outer layer of anodic oxide, the bulk of oxide, and the oxide/ GaAs interface.…”

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confidence: 99%

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Quantitative Chemical Depth Profiles of Anodic Oxide on GaAs Obtained by X‐Ray Photoelectron Spectroscopy

Mizokawa

Iwasaki

Nishitani

et al. 1979

J. Electrochem. Soc.

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The composition and structure of anodic oxides about 400Å thick grown in either 3% tartaric acid/propylene glycol or K2Cr2O7/HOCH2·CH2OH electrolytes are investigated. The ion sputtering effects are taken into account to obtain quantitative chemical depth profiles. The K2Cr2O7‐normalgrown oxide is inhomogeneous with an average Ga3+/(oxidized As) ratio of ∼3 and ∼1 in the surface region and the bulk of this oxide, respectively, while the tartaric acid‐grown oxide is homogeneous with a Ga3+/As3+ ratio of ∼1 throughout the oxide film except in the interfacial region. In the outer layer (∼100Å) of the K2Cr2O7‐normalgrown oxide, a large quantity of oxygen exists and the arsenic oxide is not As2O3 but As2O5 . In both ∼400Å thick anodic normaloxide/normalGaAs interfacial regions, whose width is ∼100Å, excess As exists and its quantity is approximately equal to the concentration difference between Ga2O3 and As2O3 in this region.

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“…The films are widely reported to be amorphous [1], though their structure may depend upon formation conditions, and to form at a nm V −1 ratio varying markedly in the range about 1.5-2.1 [2][3][4][5]. In contrast, investigations of film composition have revealed a less unified picture, with examples of relatively uniform films with atomic ratios of Ga to As > 1 [6,7], < 1 [8] and about unity [9], layered films [10] and interfacial enrichments [11][12][13]. The films are generally recognized to consist of Ga 2 O 3 and As 2 O 3 [14], although their precise distributions within the overall oxide are unclear and other species have been reported including As 2 O 5 [15,16].…”

Section: Introductionmentioning

confidence: 99%

A high-resolution, analytical study of the anodic film formed on GaAs in a tungstate electrolyte

Habazaki

Skeldon

Ghidaoui

et al. 1996

J. Phys. D: Appl. Phys.

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The anodic film formed in aqueous tungstate electrolyte at , to about 295 nm thickness, on -type GaAs at high faradaic efficiency, about 94%, has been examined by analytical transmission electron microscopy, using ultramicrotomed film sections, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, electron probe micro-analysis and scanning electron microscopy. The film is revealed to be amorphous and to comprise a uniform distribution of units of and across the main film thickness, with possible gallium enrichment in the outermost 10 nm or so of the film. Gallium and arsenic are incorporated into the anodic film at the alloy/film interface in the substrate proportions, without development of a layer enriched either in gallium or in arsenic just beneath the anodic film. The formation ratio for the film is about . The film, formed by migration both of cations and of anions across its thickness, is enriched in arsenic relative to the substrate composition, the level of enrichment suggesting that ions migrate outwards in the film about 2.4 times faster than do ions, based on a cation transport number of 0.2. The ions may be ejected, to the electrolyte, under the electric field, on reaching the film/electrolyte interface, with limited formation of an outer layer of essentially at the film/electrolyte interface, or form a layer of , up to about 10% of the total film thickness, which is thinned after anodizing by exposure to the electrolyte and the rinse water. Significantly, the outer layer of film material developed by the faster migrating ions prevents loss of ions from the film during film growth. However, during prolonged exposure to aqueous conditions in the absence of the field, the film becomes enriched in gallium species due to preferential dissolution of arsenic species. The high faradaic efficiency of film growth is a consequence of the presence of a tungsten-enriched layer, probably a gel composed of hydrated tungsten oxide, which develops at the film/electrolyte interface during film growth. No significant presence of tungsten species within the bulk of the anodic film is detected.

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Analyses of surface preparation, anodic oxidation, and epitaxial layers of GaAs using nuclear backscattering

Cited by 9 publications

References 12 publications

Character of surface states at GaAs surfaces

Character of surface states at GaAs surfaces

Quantitative Chemical Depth Profiles of Anodic Oxide on GaAs Obtained by X‐Ray Photoelectron Spectroscopy

A high-resolution, analytical study of the anodic film formed on GaAs in a tungstate electrolyte

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