Shallow donors in GaN: A magnetic double resonance investigation

Denninger, G.; Beerhalter, R.; Reiser, D.; Maier, K.; Schneider, J.; Detchprohm, Theeradetch; Hiramatsu, Kohzy

doi:10.1016/0038-1098(96)00193-7

Cited by 31 publications

(15 citation statements)

References 21 publications

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“…6(d)] we deduce a coupling constant of 1.30 MHz which is within the error limits in good agreement with the value deduced from the angular variation of the quadrupole lines. These values agree also with those previously published for as-grown materials of different origin [38,[40][41][42][43]; see also Table IV.…”

Section: Endor Measurementssupporting

confidence: 83%

Nitrogen split interstitial center(N−N)Nin GaN: High frequency EPR and ENDOR study

et al. 2014

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The nitrogen split interstitial defect introduced by high-energy particle irradiation in n-type GaN has been investigated by very high (up to 324 GHz) frequency electron paramagnetic resonance (EPR) and Q-band electron nuclear double resonance (ENDOR) spectroscopy. The increased resolution of the EPR spectra at 324 GHz has allowed us to determine the g-tensor anisotropy, which is not resolved at X or Q band. The good agreement of the principal values g xx = 1.9966, g yy = 2.0016, and g zz = 2.0036 with the theoretically predicted g tensor confirm the (N-N) N 0 defect model. The hyperfine interactions of this defect have been studied by Q-band ENDOR. We observed well-resolved ENDOR lines with distant Ga atoms from which the quadrupole coupling constants and the electrical field gradients were determined and discussed with the help of theoretical values. The observation of ENDOR spectra of the central N and Ga atoms predicted in the 20-90-MHz range required the use of field-frequency ENDOR due to the large linewidth of the ENDOR lines. Our results confirm the importance of the nitrogen split interstitial in particle irradiated GaN similar to the case of diamond and silicon carbide in which the stable configuration at room temperature of the carbon interstitials is also the split interstitial configuration.

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Section: Endor Measurementssupporting

confidence: 83%

Nitrogen split interstitial center(N−N)Nin GaN: High frequency EPR and ENDOR study

et al. 2014

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“…The absolute magnitude of the two PDOS is also eliminated as a concern, since it is the relative magnitudes at Ga and N sites that are being compared. We note that double-resonance EPR measurements of Overhauser shifts due to residual donors in h-GaN [37] provide information about the greater relative strength of the hyperfine interactions of an electron to 14 N relative to 69 Ga or 71 Ga nuclei (although the ratio given based on the Overhauser shifts can be questioned because of the neglect of the different magnetogyric ratios for the two nuclei). The hyperfine interactions reflect a spatial average over a donor hydrogenic 1s orbital, and thus cannot be directly compared to our results involving delocalized (metallic) conduction band electrons.…”

Section: Comparison Of Electronic Projected Densities Of States Atmentioning

confidence: 99%

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

et al. 2017

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We compare local electronic structure at different atom types of a metallic semiconductor in bulk and nanocrystalline form. Multinuclear magic-angle-spinning nuclear magnetic resonance (MAS NMR) establishes that GaN synthesized as an intentionally-doped bulk powder or as annealed nanocrystalline particles exhibits metallic behavior and a wide distribution of differing electronic environments in both forms. Bulk polycrystalline wurtzite GaN doped with 0.13% Ge as a shallow donor exhibits a temperature-independent distribution of 71 Ga Knight shifts over the temperature range 123-473 K. Each Knight shift frequency in the inhomogeneously-broadened spectrum is characterized by a 71 Ga spin-lattice relaxation time T 1 that is in good agreement with the value predicted by the Knight-Korringa relation across the broad range of temperatures. The14 N spectrum shows a slightly smaller Knight shift distribution with spin-lattice relaxation time T 1 values at 295 K across the distribution also in good agreement with the Knight-Korringa relation. Similarly, annealed nanocrystalline wurtzite GaN (50-100 nm, and without Ge) exhibits a 71 Ga Knight shift distribution and T 1values (at 295 K) that follow the same Knight-Korringa behavior. Thus, both bulk and nanocrystalline forms of GaN are n-type and well above the metal-insulator transition (MIT), the nanocrystals most likely as a result of incorporation of shallow donor oxygen atoms during synthesis. Carriers in both forms of sample exhibit the near-ideal characteristics of a degenerate Fermi gas of non-interacting spins. The observation of NMR signals from both atom types, Ga and N, allows for the direct spatial correlation of the local electronic structure at the two sites in the lattice, specifically the s-orbital character of the electronic wavefunction of conduction band electrons at the Fermi edge. The relative values of these carrier wavefunction probabilities (nearly twice as great for the N atom as for the Ga) are in line with theoretical predictions. Analyses of 71 Ga, 14 N, and 15 N NMR results, including double-resonance 2D 15 N{ 71 Ga} measurements, reveal electronic disorder in the form of broad distributions of local metallic properties (Knight shifts) that are shown to be spatially correlated on a sub-nanometer scale.

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“…It is a serious problem to understand with our tentative model of a Ga interstitial why the field gradients at the interstitial position and at the regular unperturbed Ga lattice site should be so similar. On the other hand a very similar electric field gradient (V zz = 6.45 x 10 20 V/m 2 ) was reported from Overhauser shift double resonance experiments on the donor [10]. A hf interaction is necessary to produce the Overhauser shift of the EPR line.…”

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confidence: 65%

Optical Detection of Electron Nuclear Double Resonance on the Residual Donor in GaN

Koschnick

Michael

Spaeth

et al. 1996

MRS Internet j. nitride semicond. res.

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Optically detected electron nuclear double resonance (ODENDOR) was measured in the 2.2 eV 'yellow' luminescence band associated with the residual donor in n-type undoped GaN. The ODENDOR lines are due to gallium and show a quadrupole splitting which can be described with an axial tensor. The quadrupole parameter was estimated to be q( 69 Ga) = 1/2 Q zz = 0.22 MHz. A hyperfine interaction for 69 Ga of about 0.3MHz for the isotropic and of about 0.15 MHz for the anisotropic part was estimated from the width of the ODENDOR lines. It is tentatively suggested that a Ga interstitial is the residual donor. Application of gallium nitride for optical devices in the near UV region requires a control of the native and extrinsic defects. Undoped MOVPE-and HVPE-grown GaN layers have high residual n-type conductivities with typically 10 17 cm -3 to 10 19 cm -3 conduction electrons, exceeding the concentrations of impurities [1] [2]. This strongly suggests that the conductivity is due to native defects. The nature of the responsible residual donor has not been identified. It is often believed to be the N vacancy [1] [2] [3]. An EPR line with a halfwidth of about 0.5 mT was observed in nominally undoped, MOVPE-grown GaN and associated with the residual donor by correlated conductivity measurements [4]. The g values of the axial g tensor were determined to be g || = 1.9515 and g^ = 1.9483. But no conclusion could be drawn from the structureless EPR line on the nature of the donor which was also observed with optically detected EPR (ODEPR) via the so called 'yellow' luminescence band at 2.2 eV [5].We report on the first optically detected electron nuclear double resonance (ODENDOR) measurements on the residual donor in GaN. The nominally undoped GaN layers were grown on sapphire with MOVPE. The ODENDOR spectra were measured in the yellow luminescence as an intensity change of the ODEPR line of the donor at 1.5 K. ODENDOR was measured with cw microwave radiation and amplitude modulation (500 Hz) of the radio frequency [6].In Figure 1 (upper trace) the ODENDOR spectrum is shown for B || c. The relative ODENDOR effect with respect to the luminescence intensity was about 2 X 10 -5 . We found ODENDOR signals only between 7 MHz and 14 MHz. The recording time of the spectrum was about 10 hours because of the extremely weak signals. The ODENDOR effect vanished for the magnetic field outside the sharp donor ODEPR resonance. Since the ODENDOR lines are centered about the Larmor frequencies of the two Ga isotopes ( 69 Ga and 71 Ga with abundancies of 60.1% and 39.9%, respectively, both with I = 3/2) it can be concluded that they are due to Ga interactions. The angular dependence of the ODENDOR spectrum is shown in Figure 2. The crystal was rotated from B || c to B ^ c in steps of 15 degrees. The peak positions of the rather broad ODENDOR lines were determined by a deconvolution of each spectrum with Gaussian lines. The squares in Figure 2 represent the positions of the line peaks. The solid lines are calculated from the spin Hamilt...

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Shallow donors in GaN: A magnetic double resonance investigation

Cited by 31 publications

References 21 publications

Nitrogen split interstitial center(N−N)Nin GaN: High frequency EPR and ENDOR study

Nitrogen split interstitial center(N−N)Nin GaN: High frequency EPR and ENDOR study

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

Optical Detection of Electron Nuclear Double Resonance on the Residual Donor in GaN

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