Chapter 13 Density-functional theory of epitaxial growth of metals

Ruggerone, Paolo; Rätsch, Christian; Scheffler, Matthias

doi:10.1016/s1571-0785(97)80016-8

Cited by 29 publications

(20 citation statements)

References 157 publications

(251 reference statements)

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“…However, the microscopic meaning of the effective parameters and the underlying microscopic processes remain unclear. In order to identify the fundamental growth mechanisms, but also to improve the above mentioned methods, the correct microscopic parameters are needed [8].We have therefore performed a comprehensive and detailed study of the migration and energetics of Ga and N adatoms on GaN surfaces, employing totalenergy density-functional theory calculations with ab initio pseudopotentials. We will focus on the two technologically relevant orientations for wurtzite GaN, the (0001) and the (0001) surfaces.…”

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Adatom diffusion at GaN (0001) and (0001̄) surfaces

Zywietz

Neugebauer

Scheffler

1998

Applied Physics Letters

459

305

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The diffusion of Ga and N adatoms has been studied for the technologically relevant wurtzite (0001) and (0001) surfaces employing density-functional theory. Our calculations reveal a very different diffusivity for Ga and N adatoms on the equilibrium surfaces: While Ga is very mobile at typical growth temperatures, the diffusion of N is by orders of magnitudes slower. These results give a very detailed insight of how and under which growth conditions N adatoms can be stabilized and efficiently incorporated at the surface. We further find that the presence of excess N strongly increases the Ga diffusion barrier and discuss the consequences for the growth of GaN.Recently, great progress in fabricating highly efficient GaN-based devices has been achieved [1,2]. Nevertheless, there are still substantial problems concerning growth optimization and insight into the fundamental mechanisms is rather shallow. Investigations of molecular beam epitaxy (MBE) growth have shown that the film structure and morphology are very sensitive to the III/V ratio [3,4]. GaN films grown under more N-rich conditions are rough and faceted while going towards more Ga-rich conditions a smoother surface morphology and better film quality are obtained [3].In order to improve growth in a systematic way it is essential to understand the underlying kinetic processes such as adsorption, desorption, and surface diffusion. In particular, adatom diffusion on surfaces is considered to be a key parameter controlling the growth rate, the material quality, and the surface morphology. Experimentally, an analysis of surface diffusion is difficult: So far only effective diffusion barriers have been obtained for GaN [4,5]. It is also not clear whether the cation or anion surface diffusion is the rate limiting process [4]. A problem in growing GaN is also the high N vapor pressure and considerable efforts have been made to enhance the N incorporation. However, the mechanism by which N is incorporated at the surface could not be identified. Theoretically, only few studies to describe GaN growth have been reported, which were either based on thermodynamic models [6] or Monte Carlo simulations [7]. These approaches are useful to model growth on a mesoscopic scale. However, the microscopic meaning of the effective parameters and the underlying microscopic processes remain unclear. In order to identify the fundamental growth mechanisms, but also to improve the above mentioned methods, the correct microscopic parameters are needed [8].We have therefore performed a comprehensive and detailed study of the migration and energetics of Ga and N adatoms on GaN surfaces, employing totalenergy density-functional theory calculations with ab initio pseudopotentials. We will focus on the two technologically relevant orientations for wurtzite GaN, the (0001) and the (0001) surfaces. The adatom substrate system is modeled by supercell geometries with at least 9 layers of GaN, a 14 bohr vacuum region and (2 × 2) periodicity. One side of the slab is passivated by fractional pseud...

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confidence: 99%

Adatom diffusion at GaN (0001) and (0001̄) surfaces

Zywietz

Neugebauer

Scheffler

1998

Applied Physics Letters

459

305

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“…14 Energy barriers for the oxygen embedment and the copper-vacancy exchange are available from previous investigations. 14,17 In the future, these energy barriers and those calculated here could be used in kinetic Monte Carlo simulations [41][42][43][44][45] to investigate length and time scales not accessible with DFT calculations. …”

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confidence: 99%

Energetics and kinetics of thec(2×2) to (22×
Lee
¹
,
McGaughey
²

2011
Phys. Rev. B
19
0
4
0
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“…an atom experiences an extra barrier in addition to the diffusion barrier when hopping down from an island [Ehrlich and Hudda (1966); Schwoebel and Shipsey (1966)]. This barrier is termed Ehrlich-Schwoebel barrier (ES-barrier) and is of the order of ∼ 0.1eV for metals [Ruggerone et al (1997)]. Intuitively the ES-barrier can be explained as follows: In order to jump down an island edge, the atom goes through a position with a lower coordination than at the saddle point of diffusion on an island.…”

Section: Growth With Ehrlich-schwoebel Barriersmentioning

confidence: 99%

Layer-By-Layer Growth for Pulsed Laser Deposition

Hinnemann¹,

Westerhoff

Wolf

2002

Phase Transitions

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Pulsed laser deposition (PLD) is a popular growth method, which has been successfully used for fabricating thin films. Compared to continuous deposition (like molecular beam epitaxy) the pulse intensity can be used as an additional parameter for tuning the growth behavior, so that under certain circumstances PLD improves layer-by-layer growth. We present kinetic Monte-Carlo simulations for PLD in the submonolayer regime and give a description of the island distance versus intensity. Furthermore we discuss a theory for second layer nucleation and the impact of Ehrlich-Schwoebel barriers on the growth behavior. We find an exact analytical expression for the probability of second layer nucleation during one pulse for high Ehrlich-Schwoebel barriers.

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Chapter 13 Density-functional theory of epitaxial growth of metals

Cited by 29 publications

References 157 publications

Adatom diffusion at GaN (0001) and (0001̄) surfaces

Adatom diffusion at GaN (0001) and (0001̄) surfaces

Energetics and kinetics of thec(2×2) to (22×
Lee
¹
,
McGaughey
²

2011
Phys. Rev. B
19
0
4
0
View full text Add to dashboard Cite

Layer-By-Layer Growth for Pulsed Laser Deposition

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Chapter 13 Density-functional theory of epitaxial growth of metals

Cited by 29 publications

References 157 publications

Adatom diffusion at GaN (0001) and (0001̄) surfaces

Adatom diffusion at GaN (0001) and (0001̄) surfaces

Energetics and kinetics of thec(2×2) to (22×Lee1, McGaughey2 2011Phys. Rev. B19040View full textAdd to dashboardCite

Layer-By-Layer Growth for Pulsed Laser Deposition

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Energetics and kinetics of thec(2×2) to (22×
Lee
¹
,
McGaughey
²

2011
Phys. Rev. B
19
0
4
0
View full text Add to dashboard Cite