<i>In</i> <i>situ</i> determination of free-carrier concentrations by reflectance difference spectroscopy

Tanaka, Hitoshi; Colas, E.; Kamiya, Itaru; Aspnes, D. E.; Bhat, R.

doi:10.1063/1.105672

Cited by 88 publications

(54 citation statements)

References 21 publications

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“…Our results are consistent with those reported in Ref. 12. Assuming that the LEO coefficient of the LT-GaAs is the same as normal GaAs, the effective surface electric field of the LT-GaAs samples, 2kV b , can then be obtained.…”

Section: ͑3͒supporting

confidence: 82%

“…Compared to that of the SI-GaAs substrate, the anisotropy spectra of the n-type GaAs shows an additional positive resonance near E 1 ϭ2.95 eV, and a negative resonance near E 1 ϩ⌬ 1 ϭ3.15 eV. This is typical of the n-type GaAs samples reported previously, 12 and is resulted from the LEO effect produced by the surface electric field. 10,11 The structures in the vicinity of E 1 and E 1 ϩ⌬ 1 for the as-grown LT-GaAs samples are similar to that of the n-type GaAs sample.…”

mentioning

confidence: 67%

“…The optical anisotropy of the SI-GaAs sample is typical and very similar to that found in other SI-GaAs substrates with even unpolished surfaces, and undoped MBE GaAs samples. It was suggested that this optical anisotropy is due to the structure anisotropy of ͑001͒ GaAs surface, 12 even when the surface is covered by an oxide layer. Compared to that of the SI-GaAs substrate, the anisotropy spectra of the n-type GaAs shows an additional positive resonance near E 1 ϭ2.95 eV, and a negative resonance near E 1 ϩ⌬ 1 ϭ3.15 eV.…”

mentioning

confidence: 99%

“…Recent RDS studies of doped GaAs showed strong anisotropy resonances at the critical points E 1 and E 1 ϩ⌬ 1 due to the electro-optic ͑LEO͒ effect generated by the surface electric field. [10][11][12] In this paper we present our RDS study of a series of LT-GaAs samples annealed at different temperatures from 300 to 850°C. Similar resonances are observed for these samples at the same GaAs critical energies.…”

mentioning

confidence: 99%

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Reflectance-difference spectroscopy study of the Fermi-level position of low-temperature-grown GaAs

Chen

Yang

et al. 1997

Phys. Rev. B

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The results of a reflectance-difference spectroscopy study of GaAs grown on ͑100͒ GaAs substrates by low-temperature molecular-beam epitaxy ͑LT-GaAs͒ are presented. In-plane optical anisotropy resonances which come from the linear electro-optic effect produced by the surface electric field are observed. The RDS line shape of the resonances clearly shows that the depletion region of LT-GaAs is indeed extremely narrow ͑Ӷ200 Å͒. The surface potential is obtained from the RDS resonance amplitude without the knowledge of space-charge density. The change of the surface potential with post-growth annealing temperatures reflects a complicated movement of the Fermi level in LT-GaAs. The Fermi level still moves for samples annealed at above 600°C, instead of being pinned to the As precipitates. This behavior can be explained by the dynamic properties of defects in the annealing process. ͓S0163-1829͑97͒51712-7͔GaAs grown by low-temperature molecular-beam epitaxy ͑LT-GaAs͒ has recently attracted much interest due to its unique properties and potential electronic and optoelectronic applications. [1][2][3][4][5] This material is crystalline, with a high content of excess arsenic, 4 which agglomerates into small metallic clusters after post-growth annealing. 5,6 With the formation of arsenic precipitates the electrical and optical properties of LT-GaAs change significantly. [3][4][5][6] For example, annealing at temperatures above 600°C usually results in LT-GaAs with extremely high resistivity. However, the mechanism of such high resistivity is still in debate. Some believe that it was the result of depletion of carriers by the Schottky barrier at the surface of the metallic As precipitates, 5,6 while others suggested a compensation model of defects similar to the conventional semi-insulating ͑SI͒ GaAs. 4 The change of carrier and defect densities inevitably changes the Fermi level, and the determination of which is therefore important in the study of defect-state evolution in post-growth annealing.Photoreflectance ͑PR͒ is extensively used to study the surface electric field and the related Fermi level of semiconductors. However, so far no Franz-Keldysh Oscillation ͑FKO͒ produced by the electric field inside LT-GaAs was ever detected except for samples annealed at above 700°C. 7,8 We believe that this is due to the highly nonuniform electric field and the extremely narrow surface depletion region which are the results of high density of defects and traps in LT-GaAs samples. 4 As a result, the Fermi level of LT-GaAs could only be determined indirectly by PR measurements of the electric field in the adjacent normal GaAs region near a LT-GaAs/ GaAs interface. 9 Here we report a direct measurement of the surface potential of LT-GaAs by reflectance-difference spectroscopy ͑RDS͒. Recent RDS studies of doped GaAs showed strong anisotropy resonances at the critical points E 1 and E 1 ϩ⌬ 1 due to the electro-optic ͑LEO͒ effect generated by the surface electric field. [10][11][12] In this paper we present our RDS study of a series of L...

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Section: ͑3͒supporting

confidence: 82%

mentioning

confidence: 67%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Reflectance-difference spectroscopy study of the Fermi-level position of low-temperature-grown GaAs

Chen

Yang

et al. 1997

Phys. Rev. B

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“…RAS has also been used to measure the SEF of GaAs via the so-called linear electro-optic effect (LEO). The LEO effect on the optical anisotropy of GaAs (001) surfaces was first observed by Acosta-Ortiz and Lastras-Martinez [14] and could be shown to depend linearly on the SEF [15][16][17]. While most investigations on the LEO effect focussed on the characterization of clean GaAs surfaces, Sobiesierski et al [18,19] investigated the LEO effect at Si d-doped GaAs (001) surfaces.…”

mentioning

confidence: 95%

Adsorbate‐induced modification of the surface electric field of GaAs (001)‐c(4 × 4) measured via the linear electro‐optic effect

Bruhn

Passmann

Fimland

et al. 2010

Physica Status Solidi (b)

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We have investigated the modification of the surface electric field (SEF) of the GaAs (001)-c(4 Â 4) surface during the adsorption of cyclopentene and 1,4-cyclohexadiene molecules by reflectance anisotropy spectroscopy (RAS) in the spectral range from 1.5 to 5.0 eV. At around 3 eV the RAS line shape originates from the so-called linear electro-optic effect (LEO). The amplitude of the LEO oscillation scales linearly with the SEF within the RAS penetration depth and is thus a measure for it. For the separation of the LEO from the RAS spectra several different methods are described in the literature. Here, we present a modified method which allows the LEO separation in particular for interfaces between GaAs and organic molecules. The results obtained this way show a significant increase of the LEO effect upon molecule adsorption indicating a higher SEF. The observed changes of the surface electronic properties are probably related to a modification of surface strain upon molecule adsorption.

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Linear Electro-Optic Photoreflectance Spectra of GaAs and CdTe around E1 and E1 + Δ1

Lastras‐Martínez¹,

Balderas‐Navarro

Cantú-Alejandro

et al. 1999

phys. stat. sol. (a)

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We report on the measurement of linear electro‐optic (LEO) photoreflectance (PR) spectra for both GaAs and CdTe (001) crystals. It is found that the amplitude of the LEO spectra is directly related to the sample doping level, while the sign of these spectra is dependent on the conductivity type of the sample. GaAs LEO spectral lineshapes, in contrast, are found to be independent of the conductivity type in the 1015 to 1017 cm—3 impurity range. These facts, along with a precise theoretical understanding of the LEO spectra, allow for the use of LEO‐PR spectroscopy for the characterization of surface and interface electric fields.

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In situ determination of free-carrier concentrations by reflectance difference spectroscopy

Cited by 88 publications

References 21 publications

Reflectance-difference spectroscopy study of the Fermi-level position of low-temperature-grown GaAs

Reflectance-difference spectroscopy study of the Fermi-level position of low-temperature-grown GaAs

Adsorbate‐induced modification of the surface electric field of GaAs (001)‐c(4 × 4) measured via the linear electro‐optic effect

Linear Electro-Optic Photoreflectance Spectra of GaAs and CdTe around E1 and E1 + Δ1

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