Oxide Passivation of Photochemically Unpinned GaAs

Kirchner, P. D.; Warren, A.C.; Woodall, J. M.; Wilmsen, C. W.; Wright, S. L.; Baker, John M.

doi:10.1149/1.2096139

Cited by 22 publications

(4 citation statements)

References 3 publications

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“…Saturation of oxide growth has been found in other oxidation techniques such as the photochemical oxidation of GaAs in water or aqueous solutions. 16,17 However, the difference of LPCEO technique from the above approaches is that the oxide film appears to be etched back after saturation. Moreover, it has also been found that the refractive index of oxide film increases obviously for long oxidation time, especially when the pH values decrease out the pH window (see the inset of Fig.…”

Section: Resultsmentioning

confidence: 99%

Effects of pH Values on the Kinetics of Liquid‐Phase Chemical‐Enhanced Oxidation of GaAs

Wang

et al. 1999

J. Electrochem. Soc.

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Due to their technological importance, native films on III-V semiconductors have been studied intensively. 1 Investigations of thermal or anodic oxides on GaAs have been performed for a number of years. [2][3][4] Many inherent problems in these two oxidation methods need to be overcome as they are applied to GaAs metal oxide semiconductor (MOS) technologies. In the case of anodic oxidation, a high electric field (ϳ5 MV/cm) in oxide films cause Ga and As atoms to diffuse through the oxide layer to the surface where they are oxidized. 5 It has also been reported that growth of anodic oxides are initiated by the reactions on the oxide surface. 6 Therefore, anodic oxidation is sensitive to contamination of the GaAs surface. As compared to the anodic method, the advantage of thermal oxidation is that it generates a fresh interface with surface contamination ending up at the oxide surface, since thermal oxidation takes place at the interface by in-diffusion of oxygen. 7 However, oxidation of GaAs proceeds very slowly below 450ЊC (<50 Å/h). 8 In addition, because the oxidation temperature exceeds the volatile temperature of As 2 O 3 , thermal oxides are composed of mostly Ga 2 O 3 . These results lead to loss of stoichiometry both in the oxide films and at the interface. At higher temperatures (>530ЊC), the films tend to crystallize and become porous, and even incongruent evaporation from substrates possibly occurs. Extensive efforts have been made to overcome this problem, such as high-pressure, 2,9 photoassisted, 10 plasma-enhanced, 11 or steam oxidation 12 methods. Among the above techniques, the required systems are complex, or the temperatures are still high.Recently, a new liquid-phase chemical-enhanced oxidation (LPCEO) technique has been proposed. 13 Neither photoenergy nor plasma source is needed. As compared to the anodic method, oxide films of GaAs can be grown near room temperature (40-70ЊC) without the assistance of electric potential. Featureless and uniform oxide films can be grown at a relatively high oxidation rate (ϳ1000 Å within an hour). In addition, good insulating and thermally stable LPCEO oxide films have been demonstrated, 14 and device applications to GaAs metal-oxide semiconductor field effect transistors (MOSFETs) have also been realized. 15 Interesting properties of the oxide growth kinetics of the LPCEO technique have been found, such as an optimum pH window for oxide growth, increase of oxide refractive index, a relatively high oxidation rate at low temperature, and etchback of oxide thickness. The experimental results indicate that the pH value of oxidation solution seems to be the dominant factor in oxide growth. In this work, the mechanisms of the Ga-containing cations as well as the role of the pH value in the LPCEO technique are investigated.Experimental Figure 1a illustrates the oxidation system which is very low cost and mainly consists of a temperature regulator and a pH meter. The flowchart of the procedure is shown in Fig. 1b. The LPCEO procedure is started with the preparation o...

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Section: Resultsmentioning

confidence: 99%

Effects of pH Values on the Kinetics of Liquid‐Phase Chemical‐Enhanced Oxidation of GaAs

Wang

et al. 1999

J. Electrochem. Soc.

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“…Surface midgap states in GaAs are known to pin the Fermi level and therefore impede the performance of metal oxide semiconductor devices − The arsenic atoms result from chemistry that occurs at the oxide/GaAs interface. Both As 2 O 3 and Ga 2 O 3 will form when a clean GaAs surface is exposed to oxygen and light.…”

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confidence: 99%

Passivation of GaAs (100) with an Adhesion Promoting Self-Assembled Monolayer

et al. 1997

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In this paper we demonstrate that photoluminescence (PL) from GaAs exposed to (3-mercaptopropyl)trimethoxysilane (MPT) exhibits a 10-fold enhancement over that of an oxidized sample. The PL enhancement is attributed to the formation of sulfur−surface bonds. We demonstrate that the MPT surface film that results from the treatment described herein is a monolayer thick by ellipsometry, and we examine the composition of the GaAs/MPT interfacial region using X-ray photoelectron spectroscopy (XPS). The XPS results indicate that the native oxide is removed by the etching procedure, and reoxidation of the surface is minimal during the subsequent deposition of MPT. The nature of the sulfur−surface bond is discussed in view of the XPS results reported here and those of previous measurements by other researchers. The self-assembled monolayers of MPT that forms on the GaAs surface leave a trimethoxy-silyl terminated surface that can be polymerized by exposure to weak acid. We demonstrate that the polymerized overlayer inhibits reoxidation of the GaAs surface better than the nonpolymerized, MPT treated surface.

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“…The light source is typically either an e l h tungsten halogen 300 W projector bulb or an argon ion laser (488 nm). During the photon illumination the GaAs is mounted on a photoresist type ' spinner and flushed with deionized water for a period which can be varied from between 10 and 103 s. As a result of this treatm ent it has been previously shown (Kirchner et a l . 1988) th at the GaAs surface is passivated with an oxide layer w chemistry is predominately Ga20 3 with only a trace of either As or As20 3, and whose thickness is an increasing function of photowash time.…”

Section: Techniques For Producing Low Surface State Densitymentioning

confidence: 99%

“…1988) th at the GaAs surface is passivated with an oxide layer w chemistry is predominately Ga20 3 with only a trace of either As or As20 3, and whose thickness is an increasing function of photowash time. For the case of p w generated oxides of greater than 5 nm thickness, a 'photoactivation' step after p w is necessary to reduce the band bending so th at an increased photoluminescence (p l ) will be seen (Wilmsen et a l . 1988).…”

Section: Techniques For Producing Low Surface State Densitymentioning

confidence: 99%

The continuing drama of the semiconductor interface

Woodall

Kirchner

Freeouf

et al. 1993

Phil. Trans. R. Soc. Lond. A

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Studies on III—V compound semiconductor surfaces and metal interfaces are discussed. For GaAs and InP surfaces aqueous photowashing or chalcogenide coatings can significantly reduce surface state densities. For metal interfaces experimental conditions have been found which lead to metal work function dominated Schottky barrier heights to GaAs. Finally, using special epilayer samples of GaAs, AlGaAs and InGaAs containing a significant excess of As, more has been learned about the origin of the invariance of the interface Fermi level (pinning) commonly observed at III—V semiconductor interfaces. The excess As can form either a high density of point defects or a dispersion of elemental As clusters depending on the post growth annealing conditions. It has been found that the pinning effects of point defects are qualitatively different from those due to the clusters of elemental As. Specifically, when the excess As is in the form of As precipitates, the As forms a Schottky barrier whose barrier height is well characterized by the parameters of As work function and semiconductor electron affinity.

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Oxide Passivation of Photochemically Unpinned GaAs

Cited by 22 publications

References 3 publications

Effects of pH Values on the Kinetics of Liquid‐Phase Chemical‐Enhanced Oxidation of GaAs

Effects of pH Values on the Kinetics of Liquid‐Phase Chemical‐Enhanced Oxidation of GaAs

Passivation of GaAs (100) with an Adhesion Promoting Self-Assembled Monolayer

The continuing drama of the semiconductor interface

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