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Onodera C.,Electronic Engineering Course
Journal of Physical Studies | Year: 2011

We investigated the effect of H 2 heat treatment on CdTe films grown on GaAs substrates by using photoluminescence (PL) and reflectance spectra. We observed the changes in heavy- and light-hole free exciton (FE) emissions and reflectance spectra with heat-treatment temperature. The energy separation between heavy-hole and light-hole FE lines calculated using the bimetallic strip model is in good agreement (4.08 meV) with that estimated from the peak energies of the heavy- and light-hole FE lines (4.0 meV). By Lorentzian deconvolution of the heavy-hole and light-hole FE lines, their widths decrease with increasing H 2 heat treatment temperature. By fitting the theoretical reflectance spectra to the measured reflectance spectra, the associated broadenings of light-hole FEs decrease with increasing H 2 heat treatment temperature. The observations suggested that the crystallinity of CdTe films is improved by H 2 heat treatment. Source


We study the effects of the exciton-longitudinal optical (LO) phonon interaction and quantum confinement on the exciton binding energies in ZnS 1-x Se x/ZnS single quantum wells (SQWs) for an Se alloy content (x) range of 0.1-0.3. In narrow ZnS 1-x Se x/ZnS SQWs, the heavy-hole (lighthole) exciton binding energy calculated by taking into account the exciton-LO phonon interaction for values of x in the range of 0.2-0.3 (0.3) exceeds the LO phonon energy of ZnS 1-x Se x. The difference between the maximum heavy-hole (light-hole) exciton binding energy for x = 0.3 and the LO phonon energy is less than 1.5 meV (1.0 meV). This SQW shows a weak quantum confinement due to a small conduction-band offset. Source


Onodera C.,Electronic Engineering Course | Shoji T.,Tohoku Institute of Technology | Taguchi T.,Yamaguchi University
Optical Review | Year: 2010

We calculate optical gain coefficient and threshold current density in ZnS/MgBeZnS quantum wells (QWs) because ZnS/MgBeZnS QWs are useful for the fabrication of an ultraviolet laser on zinc-blende substrates. The threshold current density in a ZnS/MgBeZnS QW laser diode (LD) with a 10 nm ZnS active layer is calculated to be 1.63 kA/cm2. By comparing the measured Jth in a CdZnSe/ZnSSe/ZnMgSSe QW LD with that calculated by us, it is expected that the threshold current density in ZnS/MgBeZnS QW LDs measured by experiment is larger than that calculated by our calculation method. © 2010 The Optical Society of Japan. Source


Onodera T.,Tohoku Institute of Technology | Hitomi K.,Tohoku University | Onodera C.,Electronic Engineering Course | Shoji T.,Tohoku Institute of Technology | Mochizuki K.,Ishinomaki Senshu University
IEEE Transactions on Nuclear Science | Year: 2012

Thallium bromide chloride (TlBr x Cl 1-x) crystals have been evaluated as a material used for fabrication of room temperature radiation detectors. In this study, TlBr x Cl 1-x crystals with various chlorine (Cl) concentrations were grown by the travelling molten zone method and the detectors were fabricated from the crystals. The optical properties of the crystals were evaluated by measuring the transmittances. The charge transport properties were characterized by the Hecht analysis. The band gap energy of the crystals proportionally increased with Cl concentration. Mobility-lifetime products (μm τ) of the crystals decreased with increasing Cl concentration. © 2012 IEEE. Source


We study the effects of exciton-longitudinal optical phonon interaction on the exciton binding energies in ZnS/MgxBeyZn 1-x-yS single quantum wells. The heavy- and light-hole exciton binding energies increase to the exciton-logitudinal optical phonon interaction. The increase in the maximum heavy-hole (light-hole) exciton binding energy for x = 0.74 is 68.3 meV (55.0 meV). In narrow ZnS/MgxBe yZn1-x-yS single quantum wells SQWs, the heavy- and light-hole exciton binding energies exceed the longitudinal optical phonon energy of ZnS when x ≥ 0.1. Source

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