Sulfide-passivated GaAs (001). II. Electronic properties

Paget, D.; Gusev, A. O.; Berkovits, V. L.

doi:10.1103/physrevb.53.4615

Cited by 48 publications

(27 citation statements)

References 25 publications

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“…This treatment is known to saturate Ga surface dangling bonds by sulfur atoms, and to reduce S by about one order of magnitude. 28 In order to illustrate the case of a negligibly small S (sample C), the results previously obtained for the GaInP encapsulated surface, reported in Ref. 21, are used.…”

Section: B Samplesmentioning

confidence: 99%

Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

Cadiz

Paget

Rowe

et al. 2013

Journal of Applied Physics

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For n-and p-type semiconductors doped above the 10 16 cm À3 range, simple analytical expressions for the surface recombination velocity S have been obtained as a function of excitation power P and surface state density N T . These predictions are in excellent agreement with measurements on p-type GaAs films, using a novel polarized microluminescence technique. The effect on S of surface passivation is a combination of the changes of three factors, each of which depends on N T : (i) a power-independent factor which is inversely proportional to N T and (ii) two factors which reveal the effect of photovoltage and the shift of the electron surface quasi Fermi level, respectively. In the whole range of accessible excitation powers, these two factors play a significant role so that S always depends on power. Three physical regimes are outlined. In the first regime, illustrated experimentally by the oxidized GaAs surface, S depends on P as a power law of exponent determined by N T . A decrease of S such as the one induced by sulfide passivation is caused by a marginal decrease of N T . In a second regime, as illustrated by GaInP-encapsulated GaAs, because of the reduced value of S, the photoelectron concentration in the subsurface depletion layer can no longer be neglected. Thus, S À1 depends logarithmically on P and very weakly on surface state density. In a third regime, expected at extremely small values of P, the photovoltage is comparable to the thermal energy, and S increases with P and decreases with increasing N T . V C 2013 AIP Publishing LLC. [http://dx.

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Section: B Samplesmentioning

confidence: 99%

Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

Cadiz

Paget

Rowe

et al. 2013

Journal of Applied Physics

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“…These values were confirmed by electroreflectance (ER) spectroscopy, which was also used to assess Fermi level pinning on the metal coated samples. PR is commonly used to determine the electrical properties of a semiconductor surface or interface [16 -18] or the efficacy of III-V surface passivation procedures [8,16,19]. Redistribution of charge at an interface produces an electric field across a depleted region, resulting in field dependent oscillations in the optical constants at photon energies above the band gap known as Franz-Keldysh oscillations (FKOs) [17].…”

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confidence: 99%

“…An uncoated sample which was simply removed from the MBE system and exposed to atmosphere following GaAs growth and ͑2 3 4͒-As surface termination was used as one reference sample, since the oxide͞GaAs interface has been well characterized in the past [21]. This same sample was then sulfur passivated using the wet chemical ͑NH 4 ͒ 2 S-based procedure [23], which is one of the more successful GaAs passivation procedures to date [6,7,19,24]. Finally, since the Al͞GaAs interface has also been widely studied, an Al contact sample was prepared by cooling the sample in UHV to room temperature after GaAs growth, returning it to the III-V growth chamber, and depositing a 100 Å single crystal Al(001) film.…”

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confidence: 99%

Enhanced Carrier Lifetimes and Suppression of Midgap States in GaAs at a Magnetic Metal Interface

et al. 1997

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We report the first measurement of room temperature carrier lifetimes at a magnetic metalsemiconductor interface, Fe͞GaAs͑001͒-͑2 3 4͒. The lifetimes are significantly enhanced relative to uncoated or sulfur-passivated surfaces, or the Al͞GaAs͑001͒-͑2 3 4͒ interface. These enhanced lifetimes correlate with a corresponding decrease in the density of midgap states which otherwise dominate the character of the GaAs(001) surface. The epitaxial Fe film provides both a ferromagnetic contact and a superior surface-passivating layer which does not pin the Fermi energy. [S0031-9007(97)04694-2] 73.61.Ey, 85.70.Yv Magnetic metal-semiconductor heterostructures form the basis for an emerging class of devices which derive their utility from the combination of the magnetic and electronic properties of the individual material constituents [1][2][3]. Monsma et al. [2] recently fabricated a Si metal-based transistor utilizing a (Co͞Cu) spin-valve multilayer as the base. The change in resistance of the base with applied magnetic field due to the spin-valve effect controlled the hot electron transport between the Schottky barrier emitter and collector. Datta and Das [1] proposed that a spinpolarized mode of operation could be realized in a III-V based field effect transistor (FET) by utilizing a ferromagnetic metal as the source and drain contacts, and modeled the response of the device in terms of spin-polarized transport and carrier spin precession in the high mobility twodimensional electron gas channel.The high mobility and optical properties inherent to III-V semiconductors make them especially attractive as a foundation for hybrid devices utilizing ferromagnetic layers in intimate contact with the semiconductor. However, many III-V materials are notoriously sensitive to surface/ interface effects and the formation of midgap states which result in high surface recombination velocities, decreased carrier lifetimes, and Fermi level pinning [4,5]. A great effort has been made to develop procedures which passivate the exposed surfaces of III-V materials, most notably GaAs, with some success [6][7][8].In this Letter, we report the first measurement of room temperature carrier lifetimes at a magnetic metalsemiconductor interface, Fe͞GaAs͑001͒-͑2 3 4͒. We find that the lifetimes are significantly enhanced relative to other surface terminations, and that this enhancement correlates with a significant decrease in the density of midgap states, which otherwise dominate the character of the GaAs(001) surface. We demonstrate that the epitaxial Fe film provides a ferromagnetic contact, suppresses midgap state formation, and does not pin the Fermi energy. These results have significant implications for the realization of magnetic metal-semiconductor spin transport devices. Recent calculations have shown that such states provide a very efficient mechanism for spin relaxation at the GaAs surface/interface [9]. These states are a serious impediment to successful operation of spin-dependent metalsemiconductor tunnel junctions [9] and spin-pol...

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“…Surface passivation of GaAs by thin sulfide layers produced by simple chemical solution treatments such as sodium or ammonium sulfide has been intensively investigated [4][5][6]. The sulfide passivation has been found to reduce the surface recombination velocity and surface states [7].…”

Section: Introductionmentioning

confidence: 99%

“…Based on our previous study on InP (1 0 0) [15], in present work, a well-controlled low energy S + beam was applied to treat n-GaAs (1 0 0) surface. As a way of dry sulfide passivation, the main advantages of S + ion deposition on GaAs surface as potential procedure with respect to well know solution or gas phase containing sulfur treatments applied for GaAs [4][5][6] are that it not only can avoid O 2 , CO 2 and other surface contaminations, but also can select pure S + ions, well control ion energy and ion fluency, and provide additional kinetic energy for assisting chemical reaction. Therefore, it is quite well to run the chemical reaction in comparison with the liquid or gas phase passivation procedures.…”

Section: Introductionmentioning

confidence: 99%