A quasi-white photoluminescence (PL) emission of colloidal CdS nanocrystals (NCs) of various sizes (2, 3, and 6 nm) embedded in a polymer matrix was examined by optically detected magnetic resonance (ODMR) spectroscopy. The registered ODMR spectra are complex, composed of both positive and negative signals. The positive component of the ODMR signal depends strongly on both particle size and the range of the PL wavelength registration. Based on this behavior it is ascribed to the complex paramagnetic centers formed by electron-and hole-trapping species coupled by an exchange interaction. By variation of the state of the NC/polymer interface, it is shown that the electron-trapping center is located at the interface. The sharp negative component of the ODMR spectra does not depend on the NC size. It was assigned to a sulfur vacancy (V-s) acting as a center of nonradiative recombination.

For full exploration of dilute nitrides in device applications, a better understanding and control of defects located at interfaces involving e.g. Ga(In)NP are required. In this work we report on the first identification of a point defect situated at an interface between two semiconductors: GaNP and GaP. The defect is concluded to be a complex involving a P antisite or a P interstitial in its core, partnered with a neighboring impurity/defect aligned along a <111> direction, from detailed angular dependence studies of the optically detected magnetic resonance (ODMR) spectra at both X- and Q-band microwave frequencies. The principal g and A values, g_┴=2.013, g_║=2.002, A_┴=130x10^-4 cm^-1 and A_║=330x10^-4 cm^-1, are obtained from a spin Hamiltonian analysis. The interface nature of the defect is clearly evident from the absence of the ODMR lines originating from two out of four equivalent <111> orientations. Defect formation is shown to be facilitated by severe nitrogen ion bombardment under non-equilibrium growth conditions during solid-source molecular beam epitaxy and the defect is thermally stable upon post-growth thermal annealing.

We employ the optically detected magnetic resonance (ODMR) technique to study and identify important grown-in defects in Ga(In)NP grown by molecular-beam epitaxy (MBE). Several types of defects were revealed from ODMR studies. The dominant defects were found to be related to Ga interstitials, evident form their characteristic hyperfine interaction arising from the spin interaction between the electron and the Ga nucleus. Some other as yet unidentified intrinsic defects were also found to be commonly present in the alloys. The effects of growth conditions (ion bombardment, N2 gas flow, etc.) and post-growth rapid thermal annealing on the formation of these defects were studied in detail, shedding light on the formation mechanism of defects.

By employing the optically detected magnetic resonance (ODMR) technique, two differentGa_i defects, namely Ga_i-A and Ga_i-B, are found and identifiedin the investigated Ga(Al)NAs epilayers grown on GaAs substrates bymolecular-beam epitaxy (MBE). This finding shows that Ga interstitials arecommon intrinsic defects in various dilute nitrides. In addition tothe Ga_i-related defects, “middle line” ODMR signals were observed ataround g=2 and are suggested to arise from superposition ofa defect with a single ODMR line and a defectwith an unresolved HF structure. All defects studied are shownto act as non-radiative recombination centers, and are therefore harmfulto performance of potential light-emitting devices based on the alloys.©2007 American Institute of Physics

We report on our recent results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well (QW), by the optically detected cyclotron resonance (ODCR) technique. By monitoring photoluminescence (PL) emissions from various layers the predominant ODCR peak is shown to be related to carriers with a 2D character and an effective mass of 0.51 m∗_e. The responsible carriers are ascribed to be electrons in GaAs/AlAs superlattices (SL) that are employed in the laser structures to prevent carrier leak by sandwiching the InGaNAs/GaAs QW. This conclusion is based on the following observations: (a) the ODCR peak is only observed in the structures containing the SL; (b) the effective mass value determined by the ODCR peak is independent of In and N compositions; (c) the same ODCR peak is also observed by monitoring PL from the SL. Unfortunately no ODCR signal related to InGaNAs was observed

  We report on our results from a systematic study of layered structures containing an InGaNAs/GaAs single quantum well (SQW) enclosed between staggered type II AlAs/GaAs superlattices (SL), by the photoluminescence (PL) and optically detected cyclotron resonance (ODCR) techniques. Besides the ODCR signal known to originate from electrons in GaAs, the predominant ODCR peak is shown to be related to carriers with a two-dimensional character and a cyclotron resonance effective mass of m*[approximate](0.51-0.56)m0. The responsible carriers are ascribed to electrons on the ellipsoidal equienergy surface at the AlAs X point of the Brillouin zone within the SL, based on results from angular and spectral dependences of the ODCR signal. No ODCR signal related to the InGaNAs SQW was detected, presumably due to low carrier mobility despite the high optical quality. Multiple absorption of photons with energy below the band gap energy of the SL and the GaAs barriers was observed, which bears implication on the efficiency of light-emitting devices based on these structures.

Wepresent our recent results of grown-in defects in the GaNPalloy lattice matched to Si, by optically detected magnetic resonance.One of the defects was identified as the Ga_i-B complex,commonly formed in dilute nitrides. The remaining defects are suggestedto be probably related to intrinsic defects as well.