2. Articole

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Author: search.filters.author.Gașin, PetruSubject: search.filters.subject.heterojunctions

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    THE ANALYSIS OF CURRENT FLOW MECHANISM IN CDS/CDTE HETEROJUNCTION
    (Elsevier, 2007) Vatavu, Sergiu; Gașin, Petru
    An analysis of current–voltage dependencies of CdS/CdTe heterojunction in the 78–370 K temperature range has been carried out. According to this analysis the current flow mechanism is determined by the tunneling processes through dislocations, which penetrate the heterojunction space charge region. The concentration of dislocations has been estimated as 2 · 105 cm− 2. The number of steps necessary for tunneling varies: 2.5 · 102–1.7 · 103. The characteristic energy has a weak temperature dependence (− 0.2 meV/K) and its value vary 120–200 meV. The increase of the annealing duration results in the decrease of the characteristic energy. The multistep tunneling processes through local centres, determined by impurity centres, interface states and defects in the space charge region, predominate at reverse biases. The number of tunneling steps is 1–4 · 102. The concentration of local centres (traps) in the heterojunction have been estimated as 2.37 · 105–1.63 · 106 cm− 3. The thermal annealing in the presence of CdCl2 up to 60 min does not modify the current flow mechanism in CdS/CdTe heterojunctions.
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    THE COPPER INFLUENCE ON THE PL SPECTRA OF CDTE THIN FILM AS A COMPONENT OF THE CDS/CDTE HETEROJUNCTION
    (Elsevier, 2009) Vatavu, Sergiu; Zhao, Hehong; Caraman, Iuliana; Gașin, Petru; Ferekides, Chris
    The influence of annealing in the presence of CdCl2 and a thin copper layer deposited onto CdTe on the photoluminescence spectra of CdTe, as a component of CdS/CdTe heterojunction, has been studied for two excitation wavelengths: 0.337 μm and 0.6328 μm. The behavior of the PL was studied as a function of the measurement temperature and excitation intensity. At 0.6328 μm excitation, the interface PL consists of a known 1.43X band, and the chloride annealing enhances radiative transitions at 1.536 eV. The intensity of the 1.536 eV transitions increases when Cu is present. The PL of as-deposited CdTe films prepared in the presence of oxygen has the 1.45X band attenuated when excited with 0.337 μm excitation wavelength.
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    THE INVESTIGATION OF TCO/CdS/CdTe HETEROJUNCTIONS BY C-U and C-f MEASUREMENTS: EXPERIMENT AND MODELING
    (IEEE, 2013) Rotaru, Corneliu; Vatavu, Sergiu; Fedorov, Vladimir; Gașin, Petru; Lux-Steiner, Martha; Ferekides, Chris; Rusu, Marin
    The paper presents the analysis of C-U and C-f data obtained in the 1 kHz-10 MHz range for CdS/CdTe heterojunctions prepared by CSS onto (ZnO:Al, ZnO:Al/i-ZnO)/Glass substrates. An attempt to model the physical properties of the heterojunctions is made. A small signal analysis has been carried out to establish the equivalent circuit of device. The unusual capacitance behavior of the ZnO based heterojunction is attributed to presence of the barrier at the back contact.