Analysis of trap spectra in LEC and epitaxial GaAs

Different methods of trap parameter measurement are analysed. Transient photoconductivity and thermally stimulated effects were used to investigate the influence of traps in LEC SI-GaAs and high resistivity epitaxial GaAs. The peculiarities of the TSC were analysed and shown to be related to the influence of crystal micro-inhomogeneities.Comment: Invited talk, 6-th Workshop on Gallium Arsenide and Related Compounds June 22-26, 1998 Praha-Pruhonice, Czech Republi

Influence of Structural Defects of Technological Origin on Electrical and Photoelectrical Properties of CuInSe2-ZnIn2 Se 4 Solid Solutions

Тверді розчини системи CuInSe 2 –ZnIn 2 Se 4 належать до катіонодефектних матеріалів типу B II C2 III X4, у яких край смуги власного поглинання описується правилом Урбаха. Монокристали із вмістом компоненти ZnIn2 Se 4, більшим 15 моль %, є фоточутливими при низьких температурах (T≤77 K) напівпровідниками з єдиним вузьким максимумом власної фотопровідності. Температурний коефіцієнт зміни ширини забороненої зони Eg , неза-лежно від співвідношення між компонентами твердого розчину, практично однаковий і в інтервалі температур 77300 К становить ~6·10 -4 еВ/К. Особливістю низькотемпературної фотопровідності досліджуваних сполук є підвищена фоточутливість із боку більш коротких довжин хвиль від максимуму фотопровідності. Електричні властивості монокристалів CuInSe 2 –ZnIn 2 Se 4 в області існування однофазного розчину (до 20 моль % ZnIn 2 Se 4) проявляють риси дефектних невпорядкованих систем із домінуючою стрибковою про-відністю. ; Solid solutions CuInSe 2 –ZnIn 2 Se 4 belong to cationdefective B II C III 2X4 materials in which fundamental absorption edge is described by the Urbach rule. Single crystals with a content of ZnIn 2 Se 4 more then 15 mol % turned out to be photosensitive at low temperature (T≤77 K) semiconductors with a single narrow maximum of intrinsic photoconductivity. The thermal coefficient of the variations of the width of the energy gap independently of the ratio between components of the compounds at temperatures 77300 K becomes ~6·10 -4 eV/K. The pecularity of low-temperature photoconductivity of solid solutions is increased photosensitivity at shorter wavelengths from maximum of photoconductivity. Electrical properties of crystals CuInSe 2 – ZnIn 2 Se 4 in the existence of single-phase solid solution (to ~20 mol % ZnIn 2 Se 4 ) exhibit properties of defective disordered systems with dominant hopping mechanism of conductivity

Thermal Annealing Effect on Poly(3-hexylthiophene): Fullerene:Copper-Phthalocyanine Ternary Photoactive Layer

We have fabricated poly(3-hexylthiophene) (P3HT)/copper phthalocyanine (CuPc)/fullerene (C60) ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS) photoanode and a bathocuproine (BCP)/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM) and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the I-V characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc 0.5 :C60 0.5 /BCP/Al and ITO/PEDOT:PSS/P3HT 0.3 :CuPc 0.3 :C60 0.4 /BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation

Perspectives of Portuguese People with Physical Disabilities Regarding Their Sexual Health: A Focus Group Study

The World Health Organization has considered sexual health as a major dimension of global health and a sexual right. However, the sexual health of people with physical disabilities is still poorly addressed by health and social care professionals, and it is very stigmatized by society. This study aimed to assess the perspectives of Portuguese people living with physical disabilities regarding issues affecting their sexual health. Nine women and 17 men with different physical disabilities participated in the study. Participants were recruited from a professional rehabilitation facility located in the North of Portugal and were assigned to four groups in one-hour sessions. Three main categories emerged from the content analysis: (1) meanings and beliefs regarding sexuality; (2) experiences of sexuality; (3) necessary changes. Despite the positive social changes towards sexuality, participants expressed that their sexual rights are still unfulfilled, as they live in a context that perpetuates their dependency. They pointed out low self-esteem, prejudice and social isolation, poor architectural accessibility and scarcity of financial support as some of the barriers to their lives and their sexual health. Finally, participants identified the main needs regarding their sexual health, such as: access to specialized information; training for health professionals. This study gives voice to people with physical disabilities and sheds light into both individual and contextual factors affecting their sexual health. Of utmost importance, this study draws attention to the need for reinforcing sexuality of people with disabilities in the social agenda and brings implications for future research and practice.This study was supported by a Grant attributed to the first author by the Portuguese Foundation for Science and Technology (SFRH/BD/112168/2015)info:eu-repo/semantics/publishedVersio

Defects, their interaction and modification by irradiation in semi-insulating GaAs

We investigated Semi-Insulating (SI) GaAs Schottky diode particle detectors, fabricated either on single SI-GaAs LEC crystals, or on VPE layers from several suppliers, before and after irradiation with high-energy protons and pions. A detailed comparative analysis of thermally stimulated current (TSC) and depolarisation current (TSD) spectra have been made. To separate the single traps, we used their thermal emptying by fractional heating. The following main conclusions are drawn. First of all, many different levels (from 8 by 12) have been found in the temperature range from 90 K to 300 K in all samples. Their activation energies range from 0.07 up to 0.55 eV, their capture cross sections are 10-(22) - 10(-14) cm(2), and initial occupation is 2x10(11) - 5x10(14) cm(-3). The irradiation with pions and protons does not influence the density of most levels significantly. On the other hand, levels with activation energies of about 0.07 - 0.11 CV, 0.33 - 0.36 eV, 0.4 - 0.42 eV, and 0.48 - 0.55 eV have been found only in the irradiated samples. Furthermore, peculiarities of the TSC were observed that could not be explained by a homogeneous semiconductor model. The existence of different polarisation sources in different temperature ranges is also demonstrated by TSD. It-radiation increases the inhomogeneity of the crystals, causing the scattering of the activation energies. A model of the reconstruction of dislocation net under irradiation is proposed, which foresees formation of different (p-type) conductivity channels around dislocations through the metastable transformation of the EL2 level

Ageing-dependent properties of ZnPc/C60 photovoltaic devices

The ZnPc/C60 solar cells with a reasonable energy conversion efficiency of -1.5% were investigated. The samples were aged for 1269 hours upon illumination by the blue LED with peak emission at 475nm. Upon ageing, the devices have shown a strong and fast degradation of the efficiency, short circuit current and of the fill factor within several hours followed by a much slower decrease thereof. The carrier mobility dependences on electric field strength at different temperatures were measured by the Charge Extraction by Linearly Increasing Voltage method. The observed drop of device current cannot be explained be only mobility decrease. The increase of the effective barrier height by about 0.1eV from -0.55eV up to -0.65eV was observed in the aged samples. Meanwhile, thermal activation energy values of the electrical conductivity grew from about 0.28eV prior to degradation up to about 0.34eV after ageing. © 2010 - STC "Institute for Scientific Cruystals"