Charge Trapping by Deep Donors in Si-Doped AlxGa1-xAS

1985 ◽  
Vol 46 ◽  
Author(s):  
P. M. Mooney ◽  
N. S. Caswell ◽  
P. M. Solomon ◽  
S. L. Wright
Keyword(s):  
Activation Energy ◽  
Energy Range ◽  
Charge Trapping ◽  
Lattice Relaxation ◽  
Persistent Photoconductivity ◽  
Relaxation Model ◽  
Thermally Activated ◽  
Large Lattice ◽  
Si Doped ◽  
Kinetics Of

AbstractThe kinetics of charge capture by deep donors in AlxGa1-xAs have been measured. The time dependence indicates that a single energy cannot be used to describe the trap. A model assuming thermally activated capture into a resonance in the conduction band with a range of energies gives excellent fits to the data and provides a measure of the energy range for the trap. This model is consistent with the large lattice relaxation model for DX centers. The increase of the activation energy for capture as the Al mole fraction is decreased contradicts the model which attributes the decay of the persistent photoconductivity to tunneling through the heterojunction barrier in modulationdoped structures.

Persistent photoconductivity in AlGaN films Grown by mocvd

1998 ◽  
Vol 512 ◽  
Author(s):  
A. Y. Polyakov ◽  
N. B. Smirnov ◽  
A. V. Govorkov ◽  
J. M. Redwing
Keyword(s):  
Activation Energy ◽  
Light Intensity ◽  
High Resistivity ◽  
Persistent Photoconductivity ◽  
Quasi Fermi Level ◽  
Decay Times ◽  
Long Time ◽  
Light Excitation ◽  
Si Doped ◽  
Kinetics Of

ABSTRACTPhotocurrent transients due to illumination by above-bandgap and subbandgap light were studied for Si doped and undoped films of AlGaN grown by MOCVD on sapphire and having compositions ranging from 0% to 60% of Al. It is shown that in Si doped layers the decay of photoconductivity takes extremely long time (hundreds and thousands seconds, depending on temperature, composition and illumination conditions). Both the kinetics of rise and fall of photoconductivity are best described by stretched exponents. The characteristic decay times are virtually temperature independent for temperatures below 270–290K and have activation energy of 0.14–0.26 eV (depending on composition) for higher temperatures. The decay times become longer with decreased light intensity and increase when above-bandgap light excitation is replaced by subbandgap light excitation (the photocurrent values from which the decay starts being equivalent). The results cannot be quantitatively explained by the effects of changing of the quasi-Fermi level position well known for DX-centers in AlGaAs. No persistent photoconductivity could be observed in high resistivity undoped AlGaN films with 5%, 15% and 25% of Al.

Relaxation Measurements of the Persistent Photoconductivity in Sulfur-Doped a-Si:H.

1996 ◽  
Vol 420 ◽  
Author(s):  
D. Quicker ◽  
J. Kakalios
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Sulfur Atom ◽  
Hydrogenated Amorphous Silicon ◽  
Persistent Photoconductivity ◽  
Sulfur Concentration ◽  
Illumination Time ◽  
Thermally Activated ◽  
Relaxation Measurements ◽  
Hydrogenated Amorphous

AbstractThe slow relaxation of the persistent photoconductivity (PPC) effect in sulfur-doped hydrogenated amorphous silicon (a-Si:H) has been measured as a function of temperature and illumination time. The relaxation is found to be thermally activated, with an activation energy which varies with sulfur concentration, while illuminating the film for a longer time leads to a longer relaxation time. A correlation is observed between changes of the photoconductivity during illumination and the magnitude of the PPC effect following illumination. These effects are also observed in compensated a-Si:H, suggesting that the mechanism for the PPC effect is the same in both sulfur-doped a-Si:H and compensated a-Si:H. The presence of donor and compensating acceptor states in sulfur-doped a-Si:H could arise from valence alternation pair sulfur atom defects.

Kinetics of Charge Trapping and Emission in CIGS Solar Cells

2007 ◽  
Vol 1012 ◽  
Author(s):  
Aleksander Urbaniak ◽  
Malgorzata Igalson ◽  
Susanne Siebentritt
Keyword(s):  
Solar Cells ◽  
Correlation Energy ◽  
Charge Trapping ◽  
Lattice Relaxation ◽  
Carrier Trapping ◽  
Donor And Acceptor ◽  
Cigs Solar Cells ◽  
Relaxation Time Constants ◽  
Kinetics Of

AbstractIn this work we investigate bias - induced metastability in CIGS solar cells. Long - term capacitance transients have been measured for two baseline CIGS devices with different efficiencies and a CGS cell in order to analyze carrier trapping processes. Based on the results we discuss hole emission process which leads to metastable increase of net acceptor density and also hole capture related to its relaxation. Time constants and activation energies for hole emission and capture have been obtained. Apart of carrier trapping processes we have also distinguished an interface-related change of capacitance. Our results indicate processes involving thermal lattice relaxation. We explain them in light of properties of (VSe+VCu) divacancy, defect with negative correlation energy, which can exist in both donor and acceptor configuration.

The Spin Lattice Relaxation of the Nuclear Dipolar Energy in Some Organic Crystals with Slow Molecular Motions

1969 ◽  
Vol 24 (10) ◽  
pp. 1526-1531 ◽  
Author(s):  
R. Van Steenwinkel
Keyword(s):  
Activation Energy ◽  
Molecular Diffusion ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Organic Crystals ◽  
Dipolar Relaxation ◽  
Lattice Line ◽  
Spin Lattice ◽  
Thermally Activated ◽  
Slow Motions

Abstract The relaxation of nuclear dipolar energy to the lattice has been measured in three different organic solids (benzene, cyclohexane and hexamethylbenzene) as a function of temperature. In the cases of C6H8 and C6(CH3)6 very slow motions associated with rather high activation energy were detected near the melting point. They are thought to be thermally activated rotations of the molecules about axes other than the hexad axis. In the case of cyclohexane the activation energy for the process of molecular diffusion was determined directly from the experimental results without the need of a model for vacancy diffusion. A maximum in dipolar relaxation rate was always observed for correlation times of the order of the rigid lattice line width i. e. in the temperature region where the lines narrow.

Trapping Recombination Process and Persistent Photoconductivity in Semi-Insulating 4H SiC

2006 ◽  
Vol 527-529 ◽  
pp. 563-566 ◽  
Author(s):  
Ekaterina N. Kalabukhova ◽  
S.N. Lukin ◽  
D.V. Savchenko ◽  
A.A. Sitnikov ◽  
W.C. Mitchel ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Transfer Process ◽  
Deep Trap ◽  
Persistent Photoconductivity ◽  
Charge Transfer Process ◽  
Decay Kinetics ◽  
Thermally Induced ◽  
Thermally Activated ◽  
Before And After ◽  
Kinetics Of

The decay kinetics of a persistent photoconductivity (PPC) in undoped semi-insulating 4H SiC and intercenter charge transfer were studied with EPR, photo-EPR and optical admittance spectroscopy (OAS). A thermally activated charge transfer process that occurs in the dark has been observed. The PPC effect was observed directly in changes in the quality factor of the EPR cavity before and after illumination and by the decay of the OAS signal for deep levels, and indirectly by the excitation and decay of the nitrogen and boron EPR lines that were not observed in the dark before illumination. The decay kinetics of the PPC and photo-induced carrier capture by nitrogen and boron levels were found to follow a stretched exponential form. The PPC in the temperature range from 77 to 300K was found to be produced by a thermally induced charge transfer process involving deep trap levels.

scholarly journals The transformations of the EL6 deep level defect in n-GaAs: Is EL6 a DX-like center?

1998 ◽  
Vol 510 ◽  
Author(s):  
C.V. Reddy ◽  
S. Fung ◽  
C.D. Beling
Keyword(s):  
Deep Level ◽  
Lattice Relaxation ◽  
Persistent Photoconductivity ◽  
Charge Redistribution ◽  
Deep Level Defect ◽  
Native Defects ◽  
Large Lattice ◽  
Dx Center ◽  
Low Temperature Grown Gaas ◽  
Redistribution Effect

AbstractBased on the charge redistribution effect, as observed by the present authors, and the earlier reported large lattice relaxation and persistent photoconductivity phenomena associated with the EL6 defect seen in doped, undoped, semiinsulating(SI) and low temperature grown GaAs LT-GaAs), it is suggested that this defect be classified as a DX-center. A tentative unified atomic model is proposed for all the native defects EL2, EL3, EL5, and EL6 observed in GaAs.

Persistent Photoconductivity And Thermal Recovery Kinetics Of Low Energy Ar + Bombarded GaAs

1991 ◽  
Vol 223 ◽  
Author(s):  
A. Vaseashta ◽  
L. C. Burton
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Thermal Recovery ◽  
Low Energy ◽  
Persistent Photoconductivity ◽  
Transport Parameters ◽  
Excellent Correlation ◽  
Proposed Model ◽  
Transient Spectroscopy ◽  
Kinetics Of

ABSTRACTKinetics of persistent photoconductivity, photoquenching, and thermal and optical recovery observed in low energy Ar+ bombarded on (100) GaAs surfaces have been investigated. Rate and transport equations for these processes were derived and simulated employing transport parameters, trap locations and densities determined by deep level transient spectroscopy. Excellent correlation was obtained between the results of preliminary simulation and the experimentally observed values. The exponential decay of persistent photoconductivity response curve was determined to be due to metastable electron traps with longer lifetime and is consistent with an earlier proposed model.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

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