Electron-spin-resonance studies of donors in wurtzite GaN

Carlos, W. E.; Freitas, J. A.; Khan, M. Asif; Olson, D. T.; Kuznia, J. N.

doi:10.1103/physrevb.48.17878

Cited by 136 publications

(78 citation statements)

References 31 publications

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“…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. The g-value of the broader signal (g = 1.967 ± 0.005) is close to that of a deeper donor signal (g = 1.962) detected from the 2.75 -3.1 eV spectral region of both the as-grown and annealed samples that we have studied here [10], suggesting that the same deeper donor is associated with both the 2.8 eV "blue" band and the 1.8 eV "red" band.…”

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confidence: 50%

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: 50%

Origin of the red luminescence in Mg-doped GaN

Zeng¹,

Aliev²,

Wolverson³

et al. 2006

Applied Physics Letters

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“…Several new defects are revealed from these studies, including evidence for either shallow Si or C acceptors on the N sites in the GaN homoepitaxial layers and for new deep centers in the HVPE-grown GaN. However, contrary to expectations, the reduction of random strain fields (associated with the dislocations) has not led to significant changes in the character of the magnetic resonance compared to that typically found for conventional heteroepitaxial GaN [4][5][6][7].…”

Section: Form Approved Omb No 0704-0188mentioning

confidence: 80%

“…Unfortunately, in spite of the reduced level of dislocations, no resolved hyperfine structure could be observed in the magnetic resonance of the homoepitaxial layer. The sharp feature (FWHM B2-3 mT) with g jj =1.952 and g > =1.949 is assigned to (effective-mass) shallow donors based on the previous work [4,5]. The shallow donors are likely Si on the Ga sites although residual O on the N sites may also contribute to part of this signal based on recent evidence for the shallow nature of O impurities in GaN [23].…”

Section: Gan Homoepitaxial Layersmentioning

confidence: 82%

Magnetic resonance studies of defects in GaN with reduced dislocation densities

Glaser¹,

Freitas²,

Braga³

et al. 2001

Physica B: Condensed Matter

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“…The power absorption delivered to the system is given by (15) The is the Fermi-Dirac distribution function of the electron state . We consider the term , where the line-shift in EPR spectra is and the linewidth is .…”

Section: The Response Theorymentioning

confidence: 99%

“…2, we obtain the absorption power P(B), for the spectrum of a GaN:Mn 2+ film with the out-of-plane lattice constant 5.187 Å and the bulk value 3.187 Å at T = 5 K, T = 20 K, and T = 50 K. From the magnetic field dependence of the absorption power by sweeping an external electromagnetic field, we can see the broadening effect near the resonance peak, which exhibits increase as the temperature increases. The analysis of the absorption power is very important for understanding the magnetic properties of materials [15,16]. In Fig.…”

Section: Line-profile Function For Quantum Limitmentioning

confidence: 99%

Electron Spin Transition Line-width of Mn-doped Wurtzite GaN Film for the Quantum Limit

Park¹,

Lee²,

Lee³

et al. 2012

Journal of Magnetics

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Starting with Kubo's formula and using the projection operator technique introduced by Kawabata, EPR lineprofile function for a Mn 2+-doped wurtzite structure GaN semiconductor was derived as a function of temperature at a frequency of 9.49 GHz (X-band) in the presence of external electromagnetic field. The line-width is barely affected in the low-temperature region because there is no correlation between the resonance fields and the distribution function. At higher temperature the line-width increases with increasing temperature due to the interaction of electrons with acoustic phonons. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition systems.

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Electron-spin-resonance studies of donors in wurtzite GaN

Cited by 136 publications

References 31 publications

Origin of the red luminescence in Mg-doped GaN

Origin of the red luminescence in Mg-doped GaN

Magnetic resonance studies of defects in GaN with reduced dislocation densities

Electron Spin Transition Line-width of Mn-doped Wurtzite GaN Film for the Quantum Limit

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