Nature of acceptor states in magnesium-doped gallium nitride

Aliev, G. N.; Zeng, S.; Davies, J.; Wolverson, Daniel; Bingham, S. J.; Parbrook, P. J.; Wang, T.

doi:10.1103/physrevb.71.195204

Cited by 18 publications

(31 citation statements)

References 34 publications

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“…The gvalue and width correspond closely to those of the socalled MM1 center [3,4]: this signal is PL-enhancing only when detected via the red band and has been attributed [3,4] to deep defects in the lower midgap region. At the high field side of the sharp signal two other, overlapping, luminescence-enhancing resonances are observed, which are better resolved in measurements performed at 34 GHz [10]. From comparison with previous magnetic resonance work [3,11,12,13], the narrower resonance, with g = 1.952 ± 0.003 and FWHM = 8 -10 mT, is attributed to effective-mass (EM) donors.…”

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confidence: 66%

“…3 is almost certainly oversimplified and should be viewed with caution, since energy levels other than those shown are likely to be present. Further, there is strong evidence that the depth of the shallow acceptors (presumed to be formed by substitutional magnesium at gallium sites) is affected by Jahn-Teller effects and by the influence of strain and other nearby defects [7], so that it is represented in the diagram by a range of energy levels.…”

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confidence: 99%

“…In the present work, singledetector Doppler-broadening PAS was performed using a magnetic transport positron beam system [9]. Positrons were implanted into the layers at energies in the range 0.1 -30 keV, corresponding to mean depths up to 1.5 nm.Details of the growth of the GaN:Mg samples by metallo-organic vapor phase epitaxy (MOVPE) were given earlier [7]. The Mg concentrations in the layers were not determined directly but are expected to increase monotonically with the precursor flow rate, which was 75, 100, 200 and 300 sccm for samples #626, #625, #624 and #623 respectively.…”

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confidence: 99%

“…Details of the growth of the GaN:Mg samples by metallo-organic vapor phase epitaxy (MOVPE) were given earlier [7]. The Mg concentrations in the layers were not determined directly but are expected to increase monotonically with the precursor flow rate, which was 75, 100, 200 and 300 sccm for samples #626, #625, #624 and #623 respectively.…”

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confidence: 99%

“…For a detailed description of the technique and our ODMR system, see Ref. [7]. The ODMR was carried out at 14 GHz with the specimen at 2K.…”

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Origin of the red luminescence in Mg-doped GaN

Zeng¹,

Aliev²,

Wolverson³

et al. 2006

Applied Physics Letters

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Optically-detected magnetic resonance (ODMR) and positron annihilation spectroscopy (PAS) experiments have been employed to study magnesium-doped GaN layers grown by metal-organic vapor phase epitaxy. As the Mg doping level is changed, the combined experiments reveal a strong correlation between the vacancy concentrations and the intensity of the red photoluminescence band at 1.8 eV. The analysis provides strong evidence that the emission is due to recombination in which electrons both from effective mass donors and from deeper donors recombine with deep centers, the deep centers being vacancy-related defects.Deep defects play a key role in the performance limits and aging effects of GaN-based light-emitting devices. They also lead to photoluminescence (PL) at energies well below the band-gap. For example, PL and opticallydetected magnetic resonance (ODMR) studies [1,2,3,4] have suggested that deep defects are responsible for the red (1.8 eV) luminescence band which is often observed in Mg-doped GaN and that the band is due to recombination emission in which vacancy-dopant complexes are involved [1,2]. However, this proposal was mainly based on indirect evidence and on previous experience of II -VI compounds, and further experimental confirmation is therefore needed. The present study involved the use of both ODMR and positron annihilation spectroscopy (PAS) on the same set of samples covering a range of Mg doping levels and we have established a correlation between the ODMR spectra (obtained by monitoring the red PL) and the PAS results.ODMR is well established as a means of investigating centers involved in recombination processes in semiconductors [5,6]. For a detailed description of the technique and our ODMR system, see Ref. [7]. The ODMR was carried out at 14 GHz with the specimen at 2K. The PL was excited with a UV argon-ion laser (363.8/351.1 nm). The microwaves were chopped at 605 Hz and changes in the PL intensity caused by magnetic resonance were monitored at this frequency as the magnetic field was slowly swept. PAS with a slow positron beam is an effective tool for the investigation of open volume defects such as neutral or negatively charged vacancies in semiconductor films. When positrons annihilate electrons in semiconductors the resulting gamma ray energy spectrum, peaked at 511 keV, is Doppler-broadened (since the electrons have a range of momenta). The annihilation linewidth is characterized by quantities S (W ), defined as the central (wing) fraction of the line. The value of S (W ) is characteristic of the material under study, but * Electronic address: d.wolverson@bath.ac.uk is generally higher (lower) when vacancies are present [8]. Measurements of S (W ) can thus be used to monitor vacancy concentrations. In the present work, singledetector Doppler-broadening PAS was performed using a magnetic transport positron beam system [9]. Positrons were implanted into the layers at energies in the range 0.1 -30 keV, corresponding to mean depths up to 1.5 nm.Details of the growth of the GaN:Mg sampl...

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confidence: 66%

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confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…For a detailed description of the technique and our ODMR system, see Ref. [7]. The ODMR was carried out at 14 GHz with the specimen at 2K.…”

mentioning

confidence: 99%

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Origin of the red luminescence in Mg-doped GaN

Zeng¹,

Aliev²,

Wolverson³

et al. 2006

Applied Physics Letters

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The role of vacancies in the red luminescence from Mg‐doped GaN

Zeng

Aliev

Wolverson

et al. 2006

Phys. Status Solidi (c)

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The red (1.8 eV) photoluminescence (PL) band often observed in Mg-doped GaN has been suggested to be due to a recombination process involving vacancy-related deep defects. To identify the defects concerned, optically-detected magnetic resonance (ODMR) and positron annihilation spectroscopy (PAS) experiments have been combined. A correlation between the PL spectra, the ODMR signals and the PAS data has been observed in as-grown layers as the magnesium doping level is increased. The experiments provide strong evidence that the origin of the red PL is recombination of electrons from both shallow and deep donors with holes at deep acceptors, the deep donors being complexes formed from nitrogen vacancies associated with substitutional magnesium ions and the deep acceptors being gallium vacancies or related centers.

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The magnesium acceptor states in GaN: an investigation by optically‐detected magnetic resonance

Aliev¹,

Zeng²,

Davies³

et al. 2006

Phys. Status Solidi (c)

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We observe a systematic dependence of the g-values of magnesium acceptors on the photoluminescence energy that is used for the optical detection of magnetic resonance signals. This effect leads to a model which assumes that, in the magnesium acceptors, the hole is located in an atomic orbital of p-character, presumed to be on a nitrogen atom, and which, in the wurtzite crystal field, is an orbital doublet. The remaining degeneracy is then removed by a reduction in local symmetry associated with the relative positions of the magnesium dopant and the nitrogen atom upon which the hole is localized. Further changes in the local crystal field are caused by the presence of nearby defects or by strain and are accompanied by changes in acceptor depth. The model leads to the correct g-values and the correct correlation between the g-values and acceptor depth and is consistent with a range of acceptor states of different depths being formed by simple substitution of a magnesium ion at a gallium site.

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Nature of acceptor states in magnesium-doped gallium nitride

Cited by 18 publications

References 34 publications

Origin of the red luminescence in Mg-doped GaN

Origin of the red luminescence in Mg-doped GaN

The role of vacancies in the red luminescence from Mg‐doped GaN

The magnesium acceptor states in GaN: an investigation by optically‐detected magnetic resonance

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