T. A. Kennedy

Long coherence times at 300 K for nitrogen-vacancy center spins in diamond grown by chemical vapor deposition

Electron-spin-echo experiments reveal phase-memory times as long as 58 μs at 300 K for nitrogen-vacancy centers in chemical vapor deposition (CVD) single crystals. The spins were optically polarized and optically detected. Two high-quality CVD samples were studied. From the current results, it is not clear whether these phase-memory times represent a fundamental limit or are limited by an external source of decoherence.

Electron paramagnetic resonance identification of the phosphorus antisite in electron-irradiated InP

A new electron paramagnetic resonance spectrum observed in electron‐irradiated InP is analyzed and attributed to the PIn antisite defect. The spectrum has an isotropic g value of 1.992±0.008 and a central hyperfine coupling of 0.092±0.005 cm−1 with a 100%, I= 1/2 nucleus. Irradiation conditions for the observation of PIn are described and comparison is made to antisites in GaP and GaAs.

Observation of optically detected magnetic resonance in GaN films

Optically detected magnetic resonance has been observed from GaN. Two magnetic resonances have been detected on the 2.2 eV‐deep photoluminescence band. The first resonance is sharp [full width at half‐maximum (FWHM) ∼2.2 mT] with g∥=1.9515±0.0002 and g⊥=1.9485±0.0002 and is assigned to conduction electrons, in agreement with recent electron paramagnetic resonance (EPR) studies of similar samples. The second feature, which has not been seen by EPR, is much broader (FWHM∼13 mT) with g∥=1.989±0.001 and g⊥=1.992±0.001. These parameters indicate a deep state. A tentative assignment is made to a deep state associated with the N vacancy.

Far infrared resonant magnetoabsorption in low density Si inversion layers

The density and temperature dependences of high frequency/resonant field (61.3 cm-1, 11T) resonant magnetoabsorption data in (100) Si inversion layers at low densities are strikingly different from those observed at lower frequencies/fields. The results, which include a dramatic resonant line narrowing at high fields, are discussed in light of single-electron localization and the possibility of a cooperative electronic transition assisted by the large magnetic field.

Lineshape distortions in fir cyclotron resonance of MOS structures

Abstract Cyclotron resonance lineshape distortions which include appreciable shifts in the peak position have been observed in far infrared laser transmission measurements of MOS structures. Experimental studies and a complete theoretical treatment show that these distortions arise from multiple interference effects in plane parallel sample substrates and from partial circular polarization of long wavelength coherent radiation owing to the light pipe optics.

Native defects and dopants in GaN studied through photoluminescence and optically detected magnetic resonance

Native defects and dopants in GaN grown by organometallic chemical vapor deposition have been studied with photoluminescence and optically detected magnetic resonance. For undoped samples, the combined results indicate the presence of residual shallow donors and acceptors and deep donors. A model for the capture and recombination among these defects is developed. For Mg-doped samples, the experiments reveal shallow and perturbed acceptors and shallow and deep donors. Hence, shallow and deep states for the native donor or donors appear in all samples. The Mg-acceptor is perturbed from its effective-mass state by nearby point defects.

Paramagnetic resonance in GaN‐based light emitting diodes

Significant advances in GaN‐based materials and devices have prompted intense interest in the group III nitrides. In this letter, we report electroluminescence‐detected magnetic resonance (ELDMR) and electrically detected magnetic resonance (EDMR) results on InGaN/AlGaN double heterostructures which have an intense blue emission. The dominant feature detected by either technique is a broad resonance (ΔB∼21 mT) at g≊2.00. Our ELDMR measurements show that this is associated with the blue emission and we ascribe this resonance signal to a deep Zn‐related acceptor. A second resonance, resolved in EDMR, is tentatively identified as a deep donor trap. Based on our results we propose a model for the blue emission from these diodes.

IDENTIFICATION OF VSE-IMPURITY PAIRS IN ZNSE:N

Optically detected magnetic resonance (ODMR) of heavily nitrogen‐doped ZnSe at 24 GHz reveals an anisotropic spectrum which can be assigned to a deep donor comprised of a Se vacancy paired with an impurity. The newly resolved spectrum is trigonal along 〈111〉 with g∥=2.0072(2) and g⊥=2.0013(2). Comparison of this g tensor with previous work leads to the assignment of the spectrum to VSe‐X, where X is most probably Cu or Ag. Combining this result with previous photoluminescence and ODMR work shows that ZnSe:N has three distinct donors which include both impurities and intrinsic defects.

Recombination processes in InxGa1−xN light-emitting diodes studied through optically detected magnetic resonance

Optically detected magnetic resonance (ODMR) has been observed on photoluminescence from InGaN light-emitting diodes (LEDs) under low photoexcitation conditions. The samples have the usual p-i-n structure but without etching or metallizations. Distinct ODMR features from the recombining electron and hole are found with strength that indicates significant charge separation and long lifetimes (>100 ns). The electron and hole g tensors are determined for green and extra-blue LEDs. The recombination is assigned to electrons in the InGaN quantum well (QW) and holes either bound at Mg acceptors outside the well or localized at potential minima in the QW but spatially separated from the electrons.

Detection of hydrogen in nominally pure GaP+Zn by optically detected electron nuclear double resonance

Abstract Optically detected electron nuclear double resonance (ODENDOR) measurements of the triplet antisite center P Ga 3+ in GaP:Zn have revealed the presence of hydrogen atom impurities in a nominally pure sample. Strong ligand 31 P signals have also been observed. Assuming a uniform distribution of hydrogen the intensity ratio of the 31 P to 1 H lines sets a rough lower limit of between 1–10 ppm on the hydrogen concentration. The possibility that the H 1 atoms form part of the antisite defects is also discussed.