Browsing by Author "Cuculescu, E."

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Excitonic and radiative effects in GaSe-C60 structures [Articol]
(2007) Evtodiev, Igor; Lozovanu, Petru; Cuculescu, E.; Caraman, Mihail
The absorption and photoluminescence spectra of GaSe intercalated in C60 fullerene has been investigated at 293 K and 78 K. C60 and C60-toluene molecules intercalated in-between GaSe stratified “packing” cause the appearance of localized levels revealed in low energy wing of n=1 excitonic of the absorption and determine the exciton-phonon interaction. It has been established that C60 and C60 -toluene molecules form new recombination levels in GaSe crystals and determine the 1.7÷1.75 eV photoluminescence band.
Investigation of energetic states, determined by Cu and Cd impurity atoms, at surface of GaS and GaSe monocrystalline layers [Articol]
(2007) Evtodiev, Igor; Cuculescu, E.; Postolachi, Vitalie; Caraman, Mihail
The reflection, absorption, photoconductivity, and thermally stimulated luminescence (TSL) spectra of GaS:Cu and GaSe:Cu, Cd single crystals have been studied. As a result of these investigations, the energy diagram of GaS and GaSe crystals after doping was determined.
Optical and photoelectrical characteristics of GaSe (Cu)/oxide semiconductor heterojunction [Articol]
(2008) Evtodiev, I.; Cuculescu, E.; Arama, E.; Caraman, M.
The AIIIBVI layered semiconductors are perspective materials for photoelectrical and luminescent device fabrication, for use in visible and near IR spectral region [1, 2]. GaSe and InSe semiconductors, having the bandgap equal to 2.0 eV and 1.2 eV respectively, are most often used for device fabrication [3, 4]. The applicability of GaSe crystals as a heterojunction component is limited by their low electrical conductivity (the hole concentration is ∼ 1013 cm-3 at 293 K) [5]. Cu (0.10 at %) doping of GaSe crystals causes the hole conductivity increase by more than 5 orders of magnitude and its value is ∼ (8÷9)⋅10-2Ω-1cm-1 [6]. Cu impurity atoms form two acceptor levels in GaSe positioned at 0.12 eV and 0.038 eV [1], which enlarge the applicability domain for these materials. The SnO2, In2O3 (SnO2), ZnO and others [7, 8] are used as optically transparent semiconductors in the visible and near IR spectral region and as an element of heterojunction based optoelectronic devices. This paper presents the investigation of the photoelectrical properties of GaSe (0.10 at % Cu)/ ZnO, In2O3, SnO2, Bi2O3, and Cu2O oxide semiconductor heterojunction.
Some optical properties of GaSe crystals doped with elements of group I (Li and K) [Articol]
(2008) Caraman, Mihail; Evtodiev, Igor; Cuculescu, E.
Alkaline solutions of the Li, K, andNa are used in electrical accumulators. The accumulating capacity is considerably higher comparing to technical accumulators if the principle of intercalation of the metals of group I of type AIIIBVI [1, 2] of the layered semiconductor is used. Usually variations of the compound In – Se [3] are used as electrodes. Semiconductors GaSe and GaS are not very often used as intercalated electrodes because their electrical resistivity is much higher comparing to the semiconductors InSe and modifications In2Se3.