Lattice kinetic Monte Carlo simulation study of the early stages of epitaxial GaN(0001) growth

Chugh, Manjusha; Ranganathan, Madhav

doi:10.1016/j.apsusc.2017.06.067

Cited by 23 publications

(15 citation statements)

References 49 publications

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“…Observations of triangular islands 7, 15,17 indicate that one step may grow faster, leaving behind island shapes terminated by the slower growing step. All of these features are consistent with predictions that A and B steps can have significantly different energies and/or attachment kinetics 7, 15,18,[22][23][24][25][26][27] . In particular, different attachment kinetics at A and B steps can produce a tendency to step pairing during growth and thus to different local fractions of α and β terraces.…”

Section: Introductionsupporting

confidence: 87%

Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

Ju,

Xu,

Thompson

et al. 2020

Preprint

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Images of the morphology of GaN (0001) surfaces often show half-unit-cell-height steps separating a sequence of terraces having alternating large and small widths. This can be explained by the αβαβ stacking sequence of the wurtzite crystal structure, which results in steps with alternating A and B edge structures for the lowest energy step azimuths, i.e. steps normal to [0110] type directions. Predicted differences in the adatom attachment kinetics at A and B steps would lead to alternating α and β terrace widths. However, because of the difficulty of experimentally identifying which step is A or B, it has not been possible to determine the absolute difference in their behavior, e.g. which step has higher adatom attachment rate constants. Here we show that surface X-ray scattering can measure the fraction of α and β terraces, and thus unambiguously differentiate the growth dynamics of A and B steps. We first present calculations of the intensity profiles of GaN crystal truncation rods (CTRs) that demonstrate a marked dependence on the α terrace fraction fα. We then present surface X-ray scattering measurements performed in situ during homoepitaxial growth on (0001) GaN by vapor phase epitaxy. By analyzing the shapes of the (101L) and (011L) CTRs, we determine that the steady-state fα increases at higher growth rate, indicating that attachment rate constants are higher at A steps than at B steps. We also observe the dynamics of fα after growth conditions are changed. The results are analyzed using a Burton-Cabrera-Frank model for a surface with alternating step types, to extract values for the kinetic parameters of A and B steps. These are compared with predictions for GaN (0001).

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Section: Introductionsupporting

confidence: 87%

Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

Ju,

Xu,

Thompson

et al. 2020

Preprint

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“…The standard bond-counting energetics used in a KMC study of growth on an HCP lattice 19 result in a much lower Ehrlich–Schwoebel (ES) barrier at B steps than at A steps, when only nearest-neighbor jumps are allowed. A recent KMC study of GaN (0001) growth under MBE conditions 18 found triangular islands that close analysis reveals are bounded by A steps, indicating faster growth of B steps. An analysis of InGaN (0001) growth by MBE 6 concluded that adatom attachment at B steps is faster, converting them into crenelated edges terminated by A steps.…”

Section: Introductionmentioning

confidence: 89%

In situ microbeam surface X-ray scattering reveals alternating step kinetics during crystal growth

Thompson

et al. 2021

Nat Commun

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The stacking sequence of hexagonal close-packed and related crystals typically results in steps on vicinal {0001} surfaces that have alternating A and B structures with different growth kinetics. However, because it is difficult to experimentally identify which step has the A or B structure, it has not been possible to determine which has faster adatom attachment kinetics. Here we show that in situ microbeam surface X-ray scattering can determine whether A or B steps have faster kinetics under specific growth conditions. We demonstrate this for organo-metallic vapor phase epitaxy of (0001) GaN. X-ray measurements performed during growth find that the average width of terraces above A steps increases with growth rate, indicating that attachment rate constants are higher for A steps, in contrast to most predictions. Our results have direct implications for understanding the atomic-scale mechanisms of GaN growth and can be applied to a wide variety of related crystals.

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“…See, for example, Refs. (Das and Paul, 2017;Chand et al, 2018;Dasari and Mallik, 2018;Kaur and Kashyap, 2018;Awasthi et al, 2016;Awasthi and Nair, 2017;Awasthi et al, 2018;Chugh and Ranganathan, 2016;Ghosh and Ranganathan, 2017;Chugh and Ranganathan, 2017;Sarkar et al, 2019;Maity and Reddy, 2018;Nandi et al, 2017;Hridya and Mukherjee, 2018;Sharma and Ghorai, 2018;Ahalawat and Murarka, 2017;Rout and Srinivasan, 2018;Shekar and Swathi, 2018;Kumawat and Chakrabarty, 2017;Palchowdhury and Bhargava, 2018;Mandal et al, 2018;Ahalawat and Mondal, 2018;Hasnain and Bandyopadhyay, 2015;Dutta and Nandi, 2015) for representative work from these groups in recent years. Also, many institutes now have multiple research groups working in statistical mechanics and computer simulations.…”

mentioning

confidence: 99%

“…Also, many institutes now have multiple research groups working in statistical mechanics and computer simulations. For example, at IIT Kanpur, the groups of Ranganathan and Nair are involved, respectively, in studies of surface growth and rare events using advanced simulation methods of kinetic Monte Carlo and metadynamics (Awasthi et al, 2016;Awasthi and Nair, 2017;Awasthi et al, 2018;Chugh and Ranganathan, 2016;Ghosh and Ranganathan, 2017;Chugh and Ranganathan, 2017). These groups are also actively involved in methodological developments of computer simulations using advanced theoretical techniques and computer tools.…”

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confidence: 99%

Statistical Mechanics in Theoretical Chemistry in India : Past, present and a bit of future

Chandra¹,

Bagchi²

2019

PINSA

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While the subject of statistical mechanics is intensely active in physics departments across India, with considerable activity even in mathematics departments, the same cannot be said for average chemistry departments in India where statistical mechanics is relatively less taught and even less pursued. This is to be contrasted with USA and many other developed countries (Germany, Israel) where statistical mechanics and spectroscopy are major disciplines in the physical chemistry departments. The situation, however, has changed rapidly in the past few decades. In this article we discuss the developments in this important area in the recent past, with emphasis both on analytical approach and those based on computer simulations. We also attempt to look into future problems where our efforts could be directed fruitfully.

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Lattice kinetic Monte Carlo simulation study of the early stages of epitaxial GaN(0001) growth

Cited by 23 publications

References 49 publications

Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

In situ microbeam surface X-ray scattering reveals alternating step kinetics during crystal growth

Statistical Mechanics in Theoretical Chemistry in India : Past, present and a bit of future

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