Main Spectral Feature Research Articles

Investigation of spontaneous ordering in GaInP using reflectance difference spectroscopy

Reflectance difference spectroscopy (RDS) is applied to the study of optical anisotropy in spontaneously ordered GaInP grown by metalorganic chemical-vapor deposition. The degree of ordering in GaInP has been associated previously with a shift of the band-gap energy ΔE0, and a crystal-field valence-band splitting ΔC. Theoretically and experimentally, both quantities are approximately proportional to the square of the order parameter, which varies from 0 to 1 for disordered and perfectly ordered GaInP, respectively. In this study, we examined a number of GaInP layers grown under conditions that yield a wide range of band-gap energies. The main spectral feature in all samples is a bulk-related, asymmetric peak at E0 with a long tail that extends well below E0 and a sharp, high-energy cutoff at E0+ΔC. The intensity of this peak is proportional to √ΔE0 and is therefore linear with the order parameter. By annealing GaInP in PH3/H2 mixtures, we find that the RD spectral features for energies between E0+ΔC and 3 eV are mainly surface induced. Evidence for a bulk-related RDS peak at E1 is also found.

Photoluminescence in the fractional quantum Hall regime.

For a system of coplanar electrons and holes the photoluminescence spectrum in the fractional quantum Hall regime does not exhibit anomalies associated with the fractional quantum hall effect. However, when electron and hole layers are separated, a new peak in the photoluminescence spectrum is introduced when the filling factor exceeds a fraction ${\ensuremath{\nu}}_{0}$ at which an cincompressible state occurs. The new peak is separated from the main spectral feature by the quasiparticle-quasihole gap and corresponds to a process in which a fractionally charged quasiparticle recombines with a hole, leaving behind fractionally charged quasiholes.

The electronic origin of the cool green phosphorus flame

The major electronic origin of the cool green phosphorus flame is an excited state dimer (PO) 2 * of phosphorus monoxide. A spectroscopic investigation of the gas phase oxidation of P 4 vapor in moist air has established that the visible continuum which is the main spectral feature of phosphorus chemiluminescence originates from a (PO) 2 * excimer complex. When complex formation is inhibited by increasing the reaction temperature and by diluting the reactants with buffer gas, a new emission from the electronically excited monomer appears. This emission can be assigned to the PO β-system and its appearance is kinetically and spectrally consistent with the following equilibria for the excimer: (PO) 2 * ▪ PO(X 2Π) + PO( 4Π) ▪ PO(B 2Σ +) + PO(X 2Π).