Peak Energy Variation Research Articles

Optical properties of atomically controlled InGaAs/InP quantum well structures

Atomically controlled InGaAs/InP quantum well (QW) structures are grown on (001) InP substrates at 350°C by gas source migration-enhanced epitaxy. Raman scattering measurement suggests the formation of tailored heterointerfaces: QWs having only InAs-type interfaces show the absence of Ga-P bonds, while QWs having InGaP-type interfaces indeed show the preference of Ga-P bonds. 4.2 K photoluminescence (PL) spectra for InGaAs/InP QWs show the very narrow line width comparable to the narrowest line width reported so far. PL peak energy variation with well thickness clearly depends on the heterointerface type, suggesting that the potential shifts to higher energies at the InGaP interfaces, while it drops at the InAs interfaces. Theoretical calculations assuming the formation of controlled heterointerfaces reproduce the experimentally observed PL energy variation.

Temperature dependence of free-exciton photoluminescence in crystalline GaTe.

We present a photoluminescence study of the free-exciton singlet and triplet ground states in GaTe as a function of temperature from 5 to 40 K. Over the range 5-25 K, the temperature variation of excitonic-emission linewidth and peak energy comes mainly from exciton-acoustic-phonon interactions via the deformation potential. The contribution from exciton scattering by optical phonons of energy 14 meV begins at temperatures above ∼25 K. The exciton-optical-phonon interaction is the dominant scattering process above 30 K and effectively dissociates excitons since the energy of the optical phonon mode is close to the exciton binding energy. The luminescence thus decreases rapidly above 30 K and disappears at about 40 K

Atomically controlled InGaAs/InP superlattices grown by gas source MEE (migration enhanced epitaxy)

Atomically controlled InGaAs/InP SL structures having different types of heterointerfaces are grown on (001)InP substrates at 350°C gas source MEE (migration enhanced epitaxy). RHEED intensity traces exhibit the same shape at the positions of the same type of heterointerfaces, indicating the formation of the desired heterointerfaces. The Raman spectrum from the SL, having only the InAs-type heterointerfaces, is characterized by the absence of GaP-like LO phonon clearly suggesting the formation of only the InAs-type heterointerfaces, while the SL having InGaP-type interfaces indeed shows the presence of GaP-like LO phonon peak. 4.2 K photoluminescence (PL) spectra for the InGaAs/InP quantum well (QW) structures show a very narrow line width comparable to the narrowest line width reported so far. Furthermore, the PL peak energy variation with well thickness clearly depends on the heterointerface type.

Observation of photoluminescence from InAs surface quantum wells grown on InP(100) by molecular beam epitaxy

Photoluminescence (PL) measurements are presented for surface quantum wells consisting of ultra-thin layers of InAs deposited on InP by molecular beam epitaxy. The variation of PL peak energy and intensity, with well width and temperature, clearly indicate that radiative recombination occurs within the InAs layers. Moreover, decreases in the PL emission intensities, coupled with the emergence of higher energy PL components, reflect the oxidation of the InAs surface with time.

Test of algorithm for background correction in XPS under variation of XPS peak energy

AbstractThe consistency of a recently proposed algorithm for background correction in XPS is studied, under variation of the XPS peak energy, by use of synchrotron radiation. Two approximations for the inelastic scattering properties of the solid are investigated. Both algorithms are found to account well for the variation in the inelastic scattering properties of the solid when the Au 4f XPS peak energy is varied. Small differences can be ascribed to the influence of surface excitations which are not included in the algorithm.

Variation of peak energy for energy loss with angle of observation.

The energy loss for protons on Al, Cu, and Ag thin foils around the maximum of the stopping have been measured at two different exit angles. The bombardment energy ${E}_{\mathrm{max}}$ where such a maximum occurs is found to depend on the angle of observation, ${E}_{\mathrm{max}}$ being greater when the detector is positioned off beam than when measured downstream in the beam direction. These results are discussed in terms of a varying participation of different electrons in the target. The effect of foil inhomogeneities on ${E}_{\mathrm{max}}$ is also evaluated.

Photoluminescence spectrum of p-type AlxGa1−xAs:Ge

The results of photoluminescence measurements of p-type AlxGa1−xAs:Ge (with 0.03<x<0.39) grown by liquid phase epitaxy are presented. An investigation of the composition and temperature dependencies of the acceptor-related peak in this range shows that Ge behaves as a shallow effective mass-like center. The discontinuity in the variation in peak energy versus composition that occurs at x = 0.30 is explained rather in terms of a crossing of donor levels associated with the direct and indirect band gaps. It is also shown that the luminescence is characteristic of donor-acceptor recombination involving shallow donors for x<0.30, whereas a deep donor or a vacancy complex is indicated for x≳0.30. The broad emission band at ∼1.5 eV has also been investigated but its source has not been identified. The presence of this band in the room temperature spectrum and the implications for characterization of light-emitting devices are discussed.

New observations on near band-edge luminescence in gallium arsenide phosphide (GaAs1−xPx)

We have found that the photoluminescence peak energy of n-type GaAs1−xPx crystals in the range 0.3<x<0.5 is exceptionally sensitive to the carrier concentration even in lightly doped material (< 1017 carriers cm−3). For all the crystals examined, the room-temperature photoluminescence spectrum consists of a single band corresponding to near band-edge emission. In crystals containing less than 1016 carriers cm−3, the peak energy variation with crystal composition lies close to a straight line connecting the direct band gaps of GaAs and GaP. In crystals deliberately doped with sulfur or selenium to concentrations in the 1016–1018-cm−3 range, the variation is close to the quadratic expression for band-gap variation with a bowing parameter of c =0.21.

Operating characteristics of a linear flashlamp-pumped dye laser using a coaxial dye cell

The use of a coaxial dye cell in a linear flashlamp pumped dye laser is discussed. The characteristics of the flashlamps used are reported, illustrating the variation in peak power and energy at different emission wavelengths of the xenon discharge. Thermal lensing, encountered when using a coaxial dye cell is reported and its effect on the performance of the laser demostrated.