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Trap Levels (trap + level)

Distribution by Scientific Domains
Physics and Astronomy57%
Polymers and Materials Science28%

Selected Abstracts

Photoelectrical properties of crystalline titanium dioxide thin films after thermo-annealing

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2007
R. Sathyamoorthy
Abstract This paper reports the photoelectrical properties of sol gel derived titanium dioxide (TiO2) thin films annealed at different temperatures (425-900°C). The structure of the as-grown film was found to be amorphous and it transforms to crystalline upon annealing. The trap levels are studied by thermally stimulated current (TSC) measurements. A single trap level with activation energy of 1.5 eV was identified. The steady state and transient photocurrent was measured and the results are discussed on the basis of structural transformation. The photocurrent was found to be maximum for the films annealed at 425°C and further it decreases with annealing at higher temperatures. The photoconduction parameters such as carrier lifetime, lifetime decay constant and photosensitivity were calculated and the results are discussed as a function of annealing temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electroluminescent Cu-doped CdS Quantum Dots

ADVANCED MATERIALS, Issue 28 2009
Jan W. Stouwdam
Incorporating Cu-doped CdS quantum dots into a polymer host produces efficient light-emitting diodes. The Cu dopant creates a trap level that aligns with the valence band of the host, enabling the direct injection of holes into the quantum dots, which act as emitters. At low current densities, the luminance efficiency maximizes at 9,cd A,1, providing an external quantum efficiency of 5%. [source]

Potentiometry on pentacene OFETs: Charge carrier mobilities and injection barriers in bottom and top contact configurations

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008
R. Scholz
Abstract In a combination of experimental techniques including electrical probes, potentiometry, and charge transient spectroscopy (QTS), we develop concepts how to quantify the potential drops at the contacts, the mobility in the channel region, and the density of states of deep traps in pentacene OFETs. For OFETs grown from unpurified pentacene on pre-patterned Au bottom contacts, a comparison between potentiometry and two-dimensional device simulations determines an injection barrier of 0.73 eV at the source contact and a hole mobility of 0.014 cm2 V,1 s,1 in the pentacene channel. Temperature-dependent QTS data reveal a trap level at about 125 meV from the hole transport band, indicating a relatively high density of unintentional dopants and therefore a high background density of majority charge carriers. In OFETs grown from purified pentacene onto a SiO2 gate dielectric and Au top contacts evaporated onto the pentacene channel without breaking the vacuum, potentiometry reveals a nearly perfect alignment of the metal work function with the hole transport level in the organic layer. The much lower density of deep traps in these samples raises the hole mobility to the range 0.1,0.2 cm2 V,1 s,1. A further improvement of the hole mobility and the resulting device performance can be achieved by a chemical treatment of the gate oxide with n-octadecytrichlorosilane (OTS). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Evaluating Carrier Accumulation in Degraded Bulk Heterojunction Organic Solar Cells by a Thermally Stimulated Current Technique

ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
Kenji Kawano
Abstract Here, the initial photo-degradation of encapsulated P3HT:PCBM bulk heterojunction organic solar cells is investigated. The degraded device is recovered by thermal annealing treatment. Thermally stimulated current measurements reveal that the cause of photo-degradation is carrier accumulation and that the degraded organic solar cell has two broad trap levels, of 0.71 and 0.81,eV. These traps are independent of the thickness of the photoactive layers, the mixing ratio of the photoactive materials and the cathode materials. In addition, it is confirmed that there is a close relationship between the degree of degradation and the amount of accumulated charge carriers. [source]

Low-frequency noise conversion modeling in RF devices under forced nonlinear operation

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2006
Gabriele Conte
Abstract The article addresses the frequency conversion of low-frequency noise deriving from trap-assisted generation-recombination (GR) noise in RF devices under forced, nonlinear operation through a physics-based noise model. The superposition of the stationary (small-signal) GR spectra originating from noninteracting trap levels with properly distributed energies is shown, in simple yet significant device case studies, to yield a 1/f or 1/f -like behaviour over a prescribed frequency range. The same trap distribution is also exploited for large-signal, cyclostationary noise simulation in forced periodic conditions. In this case, low-frequency 1/f -like noise is shown to be upconverted from the baseband to all noise sidebands. Circuit-level compact modeling strategies for noise-frequency conversion based on the modulation of small-signal low-frequency noise are also investigated and compared to the fundamental approach. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source]

Investigation of defects in organic semiconductors by charge based Deep Level Transient Spectroscopy (Q-DLTS)

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2009
T. P. Nguyen
Abstract We report the results of measurements of traps in light emitting devices using a new derivative of poly(phenylene vinylene) (PPV) as an active material by the charge based Deep Level Transient Spectroscopy (Q-DLTS) technique. Diodes of structure Indium Tin Oxide (ITO)/PEDOT:PSS/poly(2-ethylhexyl)surfanyl-5-methoxy phenylene vinylene (MEH-S-PPV)/M with M = Al and M = Ca/Al were investigated by measurements of current-voltage-luminance characteristics. From analysis of these characteristics, evidence of charge trapping in devices was demonstrated. The trap parameters were then determined from Q-DLTS measurements, which were carried out on the samples as a function of the charging time, the applied voltage and the temperature. Five trap levels of activation energy in the range [0.3-0.6 eV] and of density of order of 1017 cm,3 were identified in diodes with Ca/Al cathode. Electron (one level) and hole (four levels) traps were then clearly distinguished by performing measurements in hole-only devices. Trapping processes are discussed and tentatively proposed to performance of the light emitting diodes studied. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Trap states in n-GaN grown on AlN/sapphire template by MOVPE

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008
T. Ito
Abstract Using epitaxial AlN/sapphire templates, high crystalline quality GaN films are grown on them by metal organic chemical vapour deposition. The electron traps behaviour of these GaN films were observed by deep level transient spectroscopy (DLTS). Four distinct trap levels were ob-served in both n-GaN grown on AlN/sapphire template and on conventional low temperature buffer layer (LT-BL)/sapphire. The magnitude the of the DLTS signal E1 and E2 were almost same. It suggests that E1 is not only associate with dislocation density but also other defect. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]