Observation of bulk defects by scanning tunneling microscopy and spectroscopy: Arsenic antisite defects in GaAs

Feenstra, R. M.; Woodall, J. M.; Pettit, G. D.

doi:10.1103/physrevlett.71.1176

Cited by 187 publications

(156 citation statements)

References 9 publications

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“…We note that in addition to optical data, STM measurements 19 may also be helpful in the observation of BGR. We emphasize that because of the large defect and impurity content in GaMnAs, invariably present 19 in the low-temperature MBE growth of DMS materials, the observation of BGR will be complicated, but our calculated density, temperature, and magnetization dependence results should enable such a BGR observation of it is present. We also note that at finite temperature electron-phonon interaction 20 would also contribute to the BGR, but the phonon effect is smaller in magnitude than the exchange-correlation correction in the high hole density GaMnAs of interest to us.…”

Section: Discussionmentioning

confidence: 99%

Temperature and magnetization-dependent band-gap renormalization and optical many-body effects in diluted magnetic semiconductors

Zhang

Sarma

2005

Phys. Rev. B

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We calculate the Coulomb interaction induced density, temperature and magnetization dependent many-body band-gap renormalization in a typical diluted magnetic semiconductor Ga1−xMnxAs in the optimally-doped metallic regime as a function of carrier density and temperature. We find a large (∼ 0.1eV ) band gap renormalization which is enhanced by the ferromagnetic transition. We also calculate the impurity scattering effect on the gap narrowing. We suggest that the temperature, magnetization, and density dependent band gap renormalization could be used as an experimental probe to determine the valence band or the impurity band nature of carrier ferromagnetism.

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Section: Discussionmentioning

confidence: 99%

Temperature and magnetization-dependent band-gap renormalization and optical many-body effects in diluted magnetic semiconductors

Zhang

Sarma

2005

Phys. Rev. B

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“…This is consistent with the features observed for subsurface arsenic antisites As Ga in bulk LT III−V compounds. 26,27 The absence of subsurface antisites in the GaAs NWs without a LT-GaAs shell rules out the creation of antisites during the sublimation of the capping layer. Hence the antisites are incorporated during the growth of the shell at low temperature.…”

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Nonstoichiometric Low-Temperature Grown GaAs Nanowires

Álvarez

Tütüncüoǧlu

et al. 2015

Nano Lett.

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ABSTRACT:The structural and electronic properties of nonstoichiometric low-temperature grown GaAs nanowire shells have been investigated with scanning tunneling microscopy and spectroscopy, pump−probe reflectivity, and cathodoluminescence measurements. The growth of nonstoichiometric GaAs shells is achieved through the formation of As antisite defects, and to a lower extent, after annealing, As precipitates. Because of the high density of atomic steps on the nanowire sidewalls, the Fermi level is pinned midgap, causing the ionization of the subsurface antisites and the formation of depleted regions around the As precipitates. Controlling their incorporation offers a way to obtain unique electronic and optical properties that depart from the ones found in conventional GaAs nanowires.

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“…not between unit cells), indicating that they are associated with a substitutional N atom residing in the first atomic plane (i.e. the surface layer), or the third plane, or a deeper odd numbered plane [11,12]. We thus associate the observed deepest unit cells with N atoms in the first plane, and the shallower cells with N atoms in the third plane.…”

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confidence: 99%

“…Nearly the same number of each type occurs in the images. Following prior cross-sectional STM studies [11,12], we associate these two types of features with N atoms residing on different planes relative to the (1 0) surface. In the [110] direction, practically all of the dark unit cells we observe are located centrally on an anion sublattice unit cell (i.e.…”

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Arrangement of nitrogen atoms in GaAsN alloys determined by scanning tunneling microscopy

McKay

Feenstra

Schmidtling

et al. 2001

Applied Physics Letters

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The pair distribution function of nitrogen atoms in GaAs0.983N0.017 has been determined by scanning tunneling microscopy. Nitrogen atoms in the first and third planes relative to the cleaved (1 0) surface are imaged. A modest enhancement in the number of nearest-neighbor pairs particularly with [001] orientation is found, although at larger separations the distribution of N pair separations is found to be random.Considerable interest has developed in recent years concerning GaAsN and InGaAsN alloys with low N content, typically a few %. The large predicted band gap bowing in this system of highly mismatched anions leads to the possibility of considerable band gap reduction with modest N content [1,2]. Important applications include lasers with wavelength in the 1.3-1.55 µm range, as well as solar cells with band gap around 1.0 eV [3]. Generally speaking the GaAsN and InGaAsN alloys have displayed evidence of inhomogeneities, such as broad photoluminescence (PL) line widths, variable PL decay times, and short minority carrier diffusion lengths [4][5][6][7]. Such observations are often taken as an indicator of compositional fluctuations in the materials, although direct structural characterization of such fluctuations is lacking.In this work we use cross-sectional scanning tunneling microscopy (STM) to directly probe the arrangement of N atoms in GaAs 0.983 N 0.017 alloys. Nitrogen atoms of two distinct contrast levels are imaged, which we assign to occupation in the first and third surface planes relative to the (1 0) surface. From an accurate determination of the position of about 1000 N atoms in a continuous strip of alloy material, we compute the distribution function of pair separations. The arrangement of N atoms is found to be quite consistent with that expected from random occupation, with the exception that an enhanced occurrence of nearest-neighbor N pairs is found.The GaAsN alloys studied here were grown on GaAs(001) substrates by metal organic vapor phase epitaxy (MOVPE) at temperatures between 530 and 570 C using TMGa, TBAs or AsH3, and tertiarybutylhydrazine (TBHy) under hydrogen carrier gas. Additional details of the growth and characterization of the material can be found in Ref. [8]. The particular film studied here consists of a GaAs buffer layer followed by a GaAs 0.983 N 0.017 layer, a 52 nm thick GaAs spacer layer, a GaAs 0.972 N 0.028 layer, and a 370 nm thick GaAs cap layer. The thickness of the GaAsN layers was determined by high-resolution x-ray diffraction (HRXRD) to be about 18 nm; STM measurements of their thickness gave results of 14-19 nm depending on location in the wafer. The N contents quoted above were also determined by HRXRD; STM measurements for those quantities gave similar results. The GaAs substrate, buffer layer, and cap layer were doped with Si at a con-1 1°P ublished in Appl. Phys. Lett. 78, 82 (2001).

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Observation of bulk defects by scanning tunneling microscopy and spectroscopy: Arsenic antisite defects in GaAs

Cited by 187 publications

References 9 publications

Temperature and magnetization-dependent band-gap renormalization and optical many-body effects in diluted magnetic semiconductors

Temperature and magnetization-dependent band-gap renormalization and optical many-body effects in diluted magnetic semiconductors

Nonstoichiometric Low-Temperature Grown GaAs Nanowires

Arrangement of nitrogen atoms in GaAsN alloys determined by scanning tunneling microscopy

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