Determination of 2D Pair Correlations and Pair Interaction Energies of In Atoms in Molecular Beam Epitaxially Grown InGaAs Alloys

Chao, Kuo‐Jen; Shih, Chih‐Kang; Gotthold, D.; Streetman, B. G.

doi:10.1103/physrevlett.79.4822

Cited by 46 publications

(28 citation statements)

References 28 publications

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“…Figure 8 contains a set of images acquired simultaneously at −2.5 and +1.2 volts. Consistent with other STM results over InGaAs [15], first-plane In atoms appear as brighter cations in the empty state image. Several are marked with an A.…”

Section: Ingaasn Imaging and Spectroscopysupporting

confidence: 79%

“…Two of these raised areas are marked with arrows in the image. These features have been seen in previous cross-sectional STM studies of dilute InGaAs alloys where the elevated anions were thought to be pushed up by subsurface In atoms [15]. Figure 8 contains a set of images acquired simultaneously at −2.5 and +1.2 volts.…”

Section: Ingaasn Imaging and Spectroscopymentioning

confidence: 64%

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Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

McKay¹,

Feenstra²,

Schmidtling³

et al. 2001

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Nitrogen atoms in the cleaved (1 0) surfaces of dilute GaAsN and InGaAsN alloys have been studied using cross-sectional scanning tunneling microscopy. The distribution of nitrogen atoms in GaAs0.983N0.017 and In0.04Ga0.96As0.99N0.01 alloys is found to be in agreement with random statistics, with the exception of a small enhancement in the number of [001]-oriented nearest neighbor pairs. The effects of annealing on In0.04Ga0.96 As0.99N0.01 alloys has been studied by scanning tunneling spectroscopy. Spectra display a reduced band gap compared to GaAs but little difference is seen between as-grown versus annealed InGaAsN samples. In addition, voltage dependent imaging has been used to investigate second-plane nitrogen atoms.

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Section: Ingaasn Imaging and Spectroscopysupporting

confidence: 79%

Section: Ingaasn Imaging and Spectroscopymentioning

confidence: 64%

Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

McKay¹,

Feenstra²,

Schmidtling³

et al. 2001

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…3. We plot the distribution of pair separations [16] which is the observed pairs of N atoms of a specified separation divided by the number of equivalent sites of each separation (2 or 4). Uncertainties in these values are given simply by the counting statistics, and are shown on a few selected points.…”

mentioning

confidence: 99%

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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“…The existence of the short-range repulsion is clearly indicated by the fact that although clustering occurs the probability of finding a very close pair of dopant atoms is negligible. In order to quantify the repulsive interaction we deduced from the XSTM images the positions of all the dopant atoms and calculated the distances r between all possible pairs of dopants [7][8][9]. This gives us the measured probability distribution of pair distances.…”

mentioning

confidence: 99%

Importance of Many-Body Effects in the Clustering of Charged Zn Dopant Atoms in GaAs

et al. 1999

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The spatial distribution of negatively charged Zn dopant atoms in GaAs has been investigated by cross-sectional scanning tunneling microscopy. At high densities, the dopant atoms exhibit clear clustering behavior, suggesting the existence of an effective attractive interaction in addition to the screened Coulomb repulsion between two dopants. By analyzing the data through Monte Carlo simulations, we have extracted the intrinsic screening length at different dopant densities and attributed the origin of the effective attraction to strong many-body effects in the dopant-dopant repulsion.

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Determination of 2D Pair Correlations and Pair Interaction Energies of In Atoms in Molecular Beam Epitaxially Grown InGaAs Alloys

Cited by 46 publications

References 28 publications

Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

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

Importance of Many-Body Effects in the Clustering of Charged Zn Dopant Atoms in GaAs

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