0000000000793678
AUTHOR
N.v. Joshi
Detection of 4T1(P) quartet of Co2+ in Zn99.95Co0.05Se monocrystal by optical absorption spectroscopy
Abstract Optical absorption spectra of Zn 99.95 Co 0.05 Se were recorded at 25 K. The thickness and the concentration of cobalt were adjusted to obtain sharp d–d ∗ transitions of Co 2+ corresponding not only to multiplets of 4 T 1 (P) but also to higher excited states. For the first time, a very weak quartet splitting of 4 T 1 (P) state was clearly observed and these states were located between 1.464 and 1.517 eV. Higher series of energy states were found to lie in the range 1.98–2.108 eV which are expected on the basis of theoretical calculations but were not detected before and they were tentatively assigned to a lower multiplet of 2G configuration of free ion. The next series of transiti…
Study of inversion domain pyramids formed during the GaN:Mg growth
AbstractThestudyofstructuraldefectsinducedbytheintroductionofMgduringthegrowthofMOCVDGaNispresented.Themagnesiumincorporationintothecrystalgrowthnotonlyinduceschangesinthestackingsequencefromhex-agonaltocubicstructures,butalsoinvertstheGaNpolarityfromGa-facetoN-face.Basedonthedifferentsurfacestructureandsurfacemigrationlengthofabsorbingprecursorsforeachpolaritytype(Ga-orN-face),the3DgrowthontopoftheN-facetriangulardefectisdescribed.TheN-facematerialischaracterizedbythreedanglingbondsofni-trogenthatpointuptowardthec-planesurface,enhancingthecrystalgrowthalongthec-axis. 2002ElsevierScienceLtd.Allrightsreserved. Keywords:Inversiondomain;Stackingfault;Polarity 1. IntroductionFurther progress tow…
Optical study of gallium and nitrogen polarity layers of GaN grown on sapphire
A confocal Raman spectroscopic study was carried out on either side of an intentionally grown GaN inversion domain boundary between a pair of strips with opposite (Ga- or N-) polarity. It is shown that the Raman spectra on the N-polarity side displays an A1(TO) mode, prohibited by symmetry considerations, meanwhile on Ga-polarity material this peak is absent, indicating a lower density of defects present in this region. The Raman spectra reveal that in the lateral direction, the change in structural quality accross the inversion domain boundary is rather continuous and extends along 4 ± 1 μm. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Mid gap photoluminescence from GaN:Mn, a magnetic semiconductor
Abstract The defect and morphology of GaN monocrystals with Mn content 10 19 cm −3 were examined by fluorescence confocal microscopy and spectroscopy. The fluorescence spectral investigation was carried out in a region very close to the defect centers. Contrary to earlier results, we did observe a characteristic fluorescence line of Mn corresponding to the 4 T 1 → 6 A 1 and 4 T 2 → 6 A 1 transitions, suggesting the predominant presence of Mn 2+ (d 5 ). In addition, strong emission lines were observed at 1.60 and at 1.85 eV when the sample was excited with light of 436 and 365 nm, respectively. An energy scheme is proposed to explain the observed data coherently.