Surface Potential and Surface State Density in Anodized GaAs MOS Capacitors

Shimano, Akio; Moritani, Akihiro; Nakai, Junkichi

doi:10.1143/jjap.15.939

Cited by 35 publications

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“…6 the value of the Fermi level vs. conduction bandedge may be found by adding or subtracting 0.1 eV for nand p-type, respectively. The minimum in Nss for n-type material at 0.4-0.5 eV below the conduction band has been observed by others (5,6). Inspection of data for both n-and p-type samples indicates there may be a broad plateau of states in the midgap region.…”

Section: Resultssupporting

confidence: 56%

“…The method of interface state density used in our studies is much simpler than the most sensitive MOS techniques (i) used on silicon. Because the interface state density on GaAs is high (5,6), we have used the relatively insensitive (i) Terman method (7,8). For this method the donor density must be determined accurately, but with the EOS technique it is determined just before the oxide is grown.…”

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confidence: 99%

“…Differentiation of Eq [5]. with respect to Vsc leads toCo= dV---'~ --1 = Cs~ + Css [61Under depletion layer or deep depletion layer conditions, with Vsc ~ 100 mV, the space charge capacitance is related to the space charge potential drop according to the Mott-Schottky relation, which is…”

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confidence: 99%

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Electrochemical Measurements of Interface States at the GaAs / Oxide Interface

Frese

Morrison

1979

J. Electrochem. Soc.

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Electrochemical measurements are used to measure the interface state density at the GaAs/oxide interface. The techniques are described, including, for example, the use of dimethyl formamide as the solvent to avoid etching the oxide. The advantages of the "EOS" meaasurement over the standard MOS measurement are outlined and demonstrated. Several advantages are realized, stemming primarily from the fact that the inert electrolyte blocks the current flow. With the MOS technique, a conducting oxide can make the interpretation very difficult. Preliminary measurements on clean and anodically oxidized n-and p-type GaAs are presented. The interface state density is shown to be sensitive to anodization current programming and to low temperature annealing of the oxides.The measurement of the interface state density under a passivating oxide layer is important in the production of semiconductor devices. The ability to produce MOS devices depends on a low interface state density, and the development of techniques for preparing passivating layers of low interface state density depends on the ability to measure this density. Electrical techniques to measure energy on interface state levels are also valuable for understanding the chemistry of native oxide growth. For example, the SiO~/Si system is now one of the best understood oxides, primarily because of the excellent electrical methods (1) that have been developed for its study. The standard method used to study the Si/SiO~ interface involves the MOS (metal-oxide-semiconductor) configuration, where a relatively high potential applied to the metal layer induces charge at the semiconductor surface. Part of the induced charge appears in the interface states and causes a Fermi energy shift. By one of several analyses (1) based on capacity measurements, highly sensitive determinations of interface state densities down to 1010 cm -~ are possible.Measurement of interface state density at the oxidized GaAs surface has proved much more difficult (2) than the corresponding measurements at the Si/SiO~ interface. For example, high oxide leakage currents and bulk carrier trapping lead to measurement problems.An EOS (electrolyte-oxide-semiconductor) technique should have advantages that overcome many of the difficulties and permit interface state density measurement on GaAs. The two major advantages at our disposal are the use of an inert (indifferent) electrolyte and the ability to easily measure the oxide-free surface. The problem of the oxide leakage current can be prevented with the indifferent electrolyte because in this case there is an extremely low density of accessible states in the solution which can participate in electron exchange with the solid. The lack of electron exchange with the electrolyte also avoids another difficulty--the equilibrium of the interface states with the wrong Fermi energy. In fact, measurements are presented below where active ions are intentionally introduced to show that when current is allowed to flow freely across the oxide, the interface state charg...

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Section: Resultssupporting

confidence: 56%

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confidence: 99%

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Electrochemical Measurements of Interface States at the GaAs / Oxide Interface

Frese

Morrison

1979

J. Electrochem. Soc.

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“…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%

“…Wafers of p-type GaAs (p ..: 6 ,-, 12 • 10r6/cm 8) with (111) orientation were cut into disks of 5 mm diam. Before anodization, the samples were chemomechanically polished with NaOC1 and subsequently etched in a solution of 1H20 + 1H202 + 3H2SO4 for 1 min at 37~ The samples were then anodized in either of two types of electrolytic solutions; saturated nonaqueous solution of K2Cr20~/HOCH2.CH2OH (9) or 3% aqueous solution of tartaric acid mixed with propylene glycol in the ratio of 1 to 2 by volume (10). The wafers were anodized at a constant current of ,~0.4 mA/cm 2.…”

Section: Experimental Techniquesmentioning

confidence: 99%

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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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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Surface Potential and Surface State Density in Anodized GaAs MOS Capacitors

Cited by 35 publications

References 0 publications

Electrochemical Measurements of Interface States at the GaAs / Oxide Interface

Electrochemical Measurements of Interface States at the GaAs / Oxide Interface

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

Character of surface states at GaAs surfaces

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