Theory of Ga, N and H terminated GaN surfaces

Elsner, J.; Haugk, M.; Jungnickel, G.; Frauenheim, Th.

doi:10.1016/s0038-1098(98)00119-7

Cited by 41 publications

(37 citation statements)

References 14 publications

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“…The H3 configuration has an energy lower by 2.34 eV than that of the T4 configuration, which is in agreement with Refs. [12][13][14]. However, it should be noted that the increase of the supercell size to (3 × 3), the total energy difference fell down to 1.1V.…”

Section: Methodsmentioning

confidence: 95%

“…The DFT studies of the adsorption of hydrogen on GaN (0001) surface show some discrepancies which may be attributed to different methods used in the calculations [12][13][14]. Elsner et al [12] found that the 0.75 ML H coverage GaN (0001) surface has the lowest, the 0.5 ML coverage slightly higher, while full covered, (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Elsner et al [12] found that the 0.75 ML H coverage GaN (0001) surface has the lowest, the 0.5 ML coverage slightly higher, while full covered, (i.e. H-Ga site to site structure) the highest energy.…”

Section: Introductionmentioning

confidence: 99%

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Modelling the growth of nitrides in ammonia‐rich environment

Krukowski¹,

Kempisty

Strąk

et al. 2007

Cryst. Res. Technol.

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Key words gallium nitride, hydrogen vapor phase epitaxy, metal organic vapor phase epitaxy, density functional theory. PACS 61.50.Ah, 81.10.Aj Surface properties and the principal processes at the growth of gallium nitride on GaN (0001) face in ammonia-based are modeled using DFT (density functional theory -SIESTA code) ab initio calculations and 2-d diffusion analysis. The GaN growth methods are: ammonia-source MBE, MOVPE, and also HVPE. The adiabatic trajectories, calculated for hydrogen-rich and hydrogen-free state of the GaN(0001) surface, include the adsorption of NH 3 , GaCl and HCl molecules and the desorption of Ga atoms. The adsorption of ammonia and GaCl has no energy barrier. Thus, in contrast to the results concerning Plasma-Assisted Molecular Beam Epitaxy (PA MBE), proving that the GaN(0001) surface remains in metal-rich state, these results indicate that, in the ammonia-rich environment, typical for HVPE and MOVP growth, the GaN(0001) surface remains in the nitrogen-rich state. In the case of HCl adsorption, the energy barrier depends on the surface coverage, and could reach 2.0 eV. The direct desorption of single Ga atom has the energy barrier, close to 7 eV. This indicates that Ga surface diffusion (growth controlling process) length is very large, leading to strong interaction of the step kinetics and the diffusion on the terraces. This interaction leads to double-step intertwined structures both in the case of dislocation-mediated spiral growth and in the step flow growth mode. These morphologies, proposed by the geometric arguments, are observed in the atomic force microscopy (AFM) scans of the GaN(0001) surface. Additionally we have compared the interaction energy of two hydrogen atoms obtained in the DFT SIESTA and the high precision Gaussian in coupled cluster singles, double and perturbation triples CCSD(T) approximation. Both approaches yielded virtually identical interaction energy confirming the validity of DFT analysis of ammonia-rich growth of GaN.

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Section: Methodsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Modelling the growth of nitrides in ammonia‐rich environment

Krukowski¹,

Kempisty

Strąk

et al. 2007

Cryst. Res. Technol.

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“…40 On the other hand, for N-face GaN, the calculation suggested that there was always 1 ML of Ga atoms bonded to the N terminating atoms. [40][41][42] The corresponding stable oxygen coverage on N-face GaN was 0.75-1.0 ML depending on the oxygen chemical potential. 40 In this research, after the NH 3 plasma cleaning process, the experimental oxygen coverage on both Ga-and N-face GaN surface was $1 ML, which suggested oxygen was bonded to Ga atoms on both Ga-and N-face GaN.…”

Section: A Surface Composition and Oxygen Coveragementioning

confidence: 99%

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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The effects of surface pretreatment, dielectric growth, and post deposition annealing on interface electronic structure and polarization charge compensation of Ga-and N-face bulk GaN were investigated. The cleaning process consisted of an ex-situ wet chemical NH 4 OH treatment and an in-situ elevated temperature NH 3 plasma process to remove carbon contamination, reduce oxygen coverage, and potentially passivate N-vacancy related defects. After the cleaning process, carbon contamination decreased below the x-ray photoemission spectroscopy detection limit, and the oxygen coverage stabilized at $1 monolayer on both Ga-and N-face GaN. In addition, Ga-and N-face GaN had an upward band bending of 0.8 6 0.1 eV and 0.6 6 0.1 eV, respectively, which suggested the net charge of the surface states and polarization bound charge was similar on Ga-and N-face GaN. Furthermore, three dielectrics (HfO 2 , Al 2 O 3 , and SiO 2 ) were prepared by plasma-enhanced atomic layer deposition on Ga-or N-face GaN and annealed in N 2 ambient to investigate the effect of the polarization charge on the interface electronic structure and band offsets. The respective valence band offsets of HfO 2 , Al 2 O 3 , and SiO 2 with respect to Ga-and N-face GaN were 1.4 6 0.1, 2.0 6 0.1, and 3.2 6 0.1 eV, regardless of dielectric thickness. The corresponding conduction band offsets were 1.0 6 0.1, 1.3 6 0.1, and 2.3 6 0.1 eV, respectively. Experimental band offset results were consistent with theoretical calculations based on the charge neutrality level model. The trend of band offsets for dielectric/GaN interfaces was related to the band gap and/or the electronic part of the dielectric constant. The effect of polarization charge on band offset was apparently screened by the dielectric-GaN interface states. V C 2014 AIP Publishing LLC.

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“…Since we are particularly interested in consequences for growth, it is essential to take finite temperature effects into account, requiring the calculation of free energies. This distinguishes our approach from previous work in which only zerotemperature energies were calculated, and then only for a small number of structures [2][3][4]. We will show that the energetic and structural features of the surface reconstructions dramatically depend on temperature (T) and pressure (p).…”

mentioning

confidence: 93%

First-Principles Surface Phase Diagram for Hydrogen on GaN Surfaces

2002

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We discuss the derivation and interpretation of a generalized surface phase diagram, based on firstprinciples density-functional calculations. Applying the approach to hydrogenated GaN surfaces, we find that the Gibbs free energies of relevant reconstructions strongly depend on temperature and pressure. Choosing chemical potentials as variables results in a phase diagram that provides immediate insight into the relative stability of different structures. A comparison with recent experiments illustrates the power of the approach for interpreting and predicting energetic and structural properties of surfaces under realistic growth conditions. DOI: 10.1103/PhysRevLett.88.066103 PACS numbers: 68.35. -p, 68.43. -h, 81.10. -h A detailed understanding of semiconductor surface reconstructions is essential for controlling growth and materials properties. In the case of GaN, where materials quality is still limiting device progress, the investigations until now have focused on reconstructions of bare GaN surfaces [1]. The present study focuses on the role of hydrogen (H), which is important because H is abundantly present in the most commonly used growth techniques for nitride semiconductors, including metal-organic chemical vapor deposition (MOCVD), hydride vapor-phase epitaxy (HVPE), and molecular-beam epitaxy (MBE) when NH 3 is used as the nitrogen source.We have therefore performed detailed investigations of H interactions with GaN surfaces based on state-of-the-art pseudopotential-density-functional calculations. We focus on the technologically most relevant GaN(0001) surface, which is the polarity observed during MOCVD of GaN on sapphire as well as MBE on Si-face SiC. Since we are particularly interested in consequences for growth, it is essential to take finite temperature effects into account, requiring the calculation of free energies. This distinguishes our approach from previous work in which only zerotemperature energies were calculated, and then only for a small number of structures [2][3][4]. We will show that the energetic and structural features of the surface reconstructions dramatically depend on temperature (T) and pressure (p).In thermochemistry, the Gibbs free energy G is usually expressed as a function of T and partial pressures. An alternative approach is to use chemical potentials m as variables and to express G as a function of p, T, and all independent m's. For the system at hand, the Gibbs' Phase Rule produces four degrees of freedom, resulting in a four-dimensional phase space that is difficult to analyze or visualize. Our detailed analysis will show that the explicit dependence on p and T is small and can be neglected. The surface energy can then be expressed solely as a function of the chemical potentials m Ga and m H , while the p and T dependence is implicit. The advantage of this methodology is its physically intuitive character. Comparison with experiment requires only that the chemical potentials be evaluated as a function of T and partial pressures. The power of this approach will b...

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Theory of Ga, N and H terminated GaN surfaces

Cited by 41 publications

References 14 publications

Modelling the growth of nitrides in ammonia‐rich environment

Modelling the growth of nitrides in ammonia‐rich environment

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

First-Principles Surface Phase Diagram for Hydrogen on GaN Surfaces

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