Atomic structure of pyramidal defects in Mg-doped GaN

Vennéguès, P.; Leroux, M.; Dalmasso, S.; Benaı̈ssa, M.; Mierry, P. de; Lorenzini, P.; Damilano, B.; Beaumont, B.; Massies, J.; Gibart, P.

doi:10.1103/physrevb.68.235214

Cited by 83 publications

(94 citation statements)

References 25 publications

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“…vs. V "Mott-Schottky" plots) is indicative of the net charge type (donor or acceptor) beneath the surface inversion/accumulation layer [10,11]. This "turnover" occurs at lower applied bias shown to produce donors and reduce the free hole concentration; this result has been attributed to the formation of compensating defect complexes (such as Mg-V N ) [32,33] and pyramidal inversion domains [34,35]. TEM studies of Mg-doped InN, InGaN, and GaN have shown that high levels of Mg result in large densities of planar extended defects, which could also be contributing to the n-type conductivity of overdoped films [36][37][38][39].…”

Section: Electrical and Thermoelectric Measurements A Resultsmentioning

confidence: 99%

Hole transport and photoluminescence in Mg-doped InN

Miller

Ager

Smith

et al. 2010

Journal of Applied Physics

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Hole conductivity and photoluminescence were studied in Mg-doped InN films grown by molecular beam epitaxy. Because surface electron accumulation interferes with carrier type determination by electrical measurements, the nature of the majority carriers in the bulk of the films was determined using thermopower measurements. Mg concentrations in a "window" from ca. 3 × 10 17 to 1 × 10 19 cm −3 produce hole-conducting, p-type films as evidenced by a positive Seebeck coefficient. This conclusion is supported by electrolyte-based capacitance voltage measurements and by changes in the overall mobility observed by Hall effect, both of which are consistent with a change from surface accumulation on an n-type film to surface inversion on a p-type film. The observed Seebeck coefficients are understood in terms of a parallel conduction model with contributions from surface and bulk regions. In partially compensated films with Mg concentrations below the window region, two peaks are observed in photoluminescence at 672 meV and at 603 meV. They are attributed to band-to-band and band-to-acceptor transitions, respectively, and an acceptor binding energy of ∼70 meV is deduced. In hole-conducting films with Mg concentrations in the window region, no photoluminescence is observed; this is attributed to electron trapping by deep states which are empty for Fermi levels close to the valence band edge. * Corresponding author: JWAger@lbl.gov

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Section: Electrical and Thermoelectric Measurements A Resultsmentioning

confidence: 99%

Hole transport and photoluminescence in Mg-doped InN

Miller

Ager

Smith

et al. 2010

Journal of Applied Physics

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“…For large Mg concentrations, however, high densities of extended defects have been reported, such as Mg induced pyramidal defects [10][11][12], extended facetted defects [5,13,14], and nanotubes [15]. A common building blocks of all these defects is given by inversion domain boundaries [14,[16][17][18] where Mg is agglomerated, leading to a decrease of the hole concentration. It has been proposed that such defects arise from Mg surface segregation and they form as soon as a the local Mg concentration near the surface exceeds a certain threshold concentration [12].…”

Section: â 10mentioning

confidence: 99%

“…All these defects include inversion domain boundaries with local Mg enrichment [14,[16][17][18]. A cross-sectional transmission electron micrograph of one of the samples investigated with XSW is shown in Fig.…”

Section: Incorporation and Defects 41 Mg Doped Filmsmentioning

confidence: 99%

Mg and Si dopant incorporation and segregation in GaN

Schmidt

Siebert

Flege

et al. 2011

Physica Status Solidi (b)

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The surface segregation of Mg and Si dopant species and their atomic incorporation sites in GaN films grown by metal-organic vapour phase epitaxy (MOVPE) on sapphire (0001) substrates have been analysed by X-ray photoemission spectro-microscopy and X-ray standing waves (XSW). As revealed by spectro-microscopy, both Mg and Si tend to segregate to the surface. In case of Mg, an enhanced surface dopant concentration is found even after sputter-removal of several tens of nanometres, which confirms a segregation mechanism proposed earlier [S. Figge et al., Appl. Phys. Lett. 81, 4748 (2002)]. Si doping has been found to result in the formation of facetted grooves in the GaN films. The surface silicon concentration at the facets is determined to be about 2.5 times higher as compared to the planar (0001) surface by micro-spectroscopy. XSW results show that with increasing Mg dopant concentration, non-substitutional lattice sites are progressively occupied. The results can quantitatively be explained by Mg atoms incorporated in an anti-bixbyite-like structure and is related to inversion domain boundaries. For Si doping, no evidence is found for the occupation of non-substitutional sites. However, a decrease in crystal quality is observed with increasing Si concentration.X-ray photoemission micrograph of a Si doped GaN film showing a facetted groove at the lower left corner of the image. The local spectra (see inset) reveal Si enrichment at the facets.

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“…Presence of such holes was also confirmed by positron annihilation study [7]. Since these defects were also described as inversion domains [8] or Mg 3 N 2 precipitates [9] high resolution focal series for focal-series reconstruction of the electron exit-surface wave (ESW) leaving the specimen were applied for these studies [10].…”

Section: Tem Studies Of Defects In Bulk and Mocvd Grown Gan:mg Layersmentioning

confidence: 93%

Atomic structure of pyramidal defects in GaN:Mg: Influence of annealing

Liliental‐Weber¹,

Tomaszewicz

Zakharov

et al. 2006

Physica Status Solidi (a)

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Abstract:The atomic structure of the characteristic defects (Mg-rich hexagonal pyramids) in pdoped bulk and MOCVD GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects, confirmed also with positron annihilation. The inside walls of the cavities were covered by GaN of reverse polarity compared to the matrix. Defects in bulk GaN:Mg were almost one order of magnitude larger than in thin films. An exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6±0.2Å displacement between the Ga sublattices of these two areas. A [1100]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid was observed. Annealing of the MOCVD layers lead to slight increase of the defect size and an increase of the photoluminescence intensity. Positron annihilation confirms presence of vacancies of different sizes triggered by the Mg doping in as-grown samples and decrease of their concentration upon annealing at 900 and 1000°C.

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Atomic structure of pyramidal defects in Mg-doped GaN

Cited by 83 publications

References 25 publications

Hole transport and photoluminescence in Mg-doped InN

Hole transport and photoluminescence in Mg-doped InN

Mg and Si dopant incorporation and segregation in GaN

Atomic structure of pyramidal defects in GaN:Mg: Influence of annealing

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