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Hartree–Fock ab initio Raman spectra calculations and Raman spectroscopic measurements were carried out on amorphous selenium in order to identify the characteristic vibrational mode due to sigma bonds. Variations in measured peak intensity were observed as a consequence of band gap light illumination. Based on our previous theoretical investigations we originate these intensity variations from photoinduced covalent bond breaking. [ABSTRACT FROM AUTHOR]

Atomic scale computer simulations on structures and photoinduced volume changes of flatly and obliquely deposited amorphous selenium (a-Se) films have been carried out in order to understand how the properties of chalcogenide glasses are influenced by their preparation method. Obliquely deposited a-Se thin films contain more coordination defects and larger voids than the flatly deposited ones. To model the photoinduced volume changes the electron excitation and hole creation were treated independently within the framework of tight-binding formalism. Covalent and interchain bond breakings and formations were found. The obliquely deposited samples containing voids showed a wide spectrum of photoinduced structural changes in the microscopic level and volume changes in the macroscopic level. [ABSTRACT FROM AUTHOR]

Using the recently discovered time-dependent spin-orbit-photon interaction operator and first order perturbation theory, the rate of spontaneous emission from triplet excitations is derived within the two-level approximation for organic molecular solids and conjugated polymers. The calculated rates and corresponding radiative lifetimes agree very well with the known experimental results. Present results are compared with those obtained through the traditional approach of the second order perturbation theory in some molecular crystals and found to be in better agreement with experiments. [ABSTRACT FROM AUTHOR]

Presents a study which investigated aluminum gallium arsenide/gallium arsenide heterostructure field-effect transistors by noise measurements. Model for calculating the trap concentration in highly doped semiconductors; Evaluation of the activation energies of the traps and the trap concentration; Spectrum of generation-recombination noise.

Provides information on an experiment which investigated the processes leading to light-output reduction after short-term degradation of test samples of GaP:N light emitting diodes (LEDs). Methodology used to conduct the experiment; Observations of the deep level transient spectroscopy (DLTS); Preparation of the chips of GaP structures; Findings of the experiment.

Examines the p-type AlGaAs/GaAs heterostructures by means of photoconductivity and low-frenquency noise measurements. Sequence of the layers grown by molecular-beam epitaxy on semi-insulating GaAs substrates; Noise measurements under constant current conditions; Conclusion.

Deep level analysis in the ohmic regime of ungated n-InGaAs/p-InP junction field-effect transistor structures was made by low-frequency noise measurements. The noise spectra exhibit two deep trap levels in the n-InGaAs channel with activation energies of 0.49 and 0.37 eV. The related capture cross sections are 7×10-15 and 4×10-16 cm2, respectively. [ABSTRACT FROM AUTHOR]

Using the recently discovered time-dependent spin-orbit-photon interaction operator and first order perturbation theory, the rate of spontaneous emission from triplet excitations is derived within the two-level approximation for organic molecular solids and conjugated polymers. The calculated rates and corresponding radiative lifetimes agree very well with the known experimental results. Present results are compared with those obtained through the traditional approach of the second order perturbation theory in some molecular crystals and found to be in better agreement with experiments.