Light-Induced Metastable Changes in a-SiSx:H

1995 ◽  
Vol 377 ◽  
Author(s):  
S. L. Wang ◽  
P. C. Taylor
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Annealing Temperature ◽  
Dark Conductivity ◽  
Sulfur Concentration ◽  
Thermally Activated ◽  
Dramatic Difference ◽  
The Creation ◽  
Sulfur Donor

ABSTRACTMetastable light-induced increases in the dark conductivities of a-SiSx:H alloys are explained as photo-activation of hydrogen-passivated sulfur donor sites. For a sulfur concentration (sulfur-to-silicon ratio) of 5.6 × 103 the excess dark conductivity as a function of illumination temperature is thermally activated with an activation energy of 0.72 eV. When the sulfur concentration is 3.3 × 102, the temperature dependence is very weak. This dramatic difference in the temperature dependence of the creation of increased dark conductivity is explained by a lowering of the annealing temperature for the metastable changes as the sulfur concentration increases. We discuss the influence of this new metastability on the possibility of obtaining more stable films.

Metastable Defect Kinetics in Hydrogen Passivated Polycrystalline Silicon

1994 ◽  
Vol 336 ◽  
Author(s):  
N. H. Nickel ◽  
R. A. Street ◽  
W. B. Jackson ◽  
N. M. Johnson
Keyword(s):  
Temperature Dependence ◽  
Polycrystalline Silicon ◽  
Direct Evidence ◽  
Slow Cool ◽  
Dark Conductivity ◽  
Active Hydrogen ◽  
Thermally Activated ◽  
Rate Dependent ◽  
Si Films ◽  
Metastable Defect

ABSTRACTThe temperature dependence of the dark conductivity, σD, of unhydrogenated and hydrogen passivated polycrystalline silicon (poly-Si) films was Measured. While σD of unhydrogenated poly-Si did not exhibit any influence of thermal treatment prior to the measurement, striking effects were observed in hydrogenated poly-Si films. Below 268 K a cooling-rate dependent metastable change of σD is observed. The dark conductivity increases by more than 8 orders of magnitude. This frozen-in state is metastable: Annealing and a slow cool restore the temperature dependence of the relaxed state. The time and temperature dependence of the relaxation reveal that this process is thermally activated with 0.74 eV. The lack of the quenching metastability in unhydrogenated poly-Si is direct evidence that the metastable changes in σD are due to the formation and dissociation of an electrically active hydrogen complex, in the grain-boundary regions.

Temperature Dependence of Cathodoluminescence From InxGa1-xAs/GaAs Multiple Quantum Wells

1995 ◽  
Vol 379 ◽  
Author(s):  
K. Rammohan ◽  
D.H. Rich ◽  
A. Larsson
Keyword(s):  
Activation Energy ◽  
Quantum Wells ◽  
Temperature Dependence ◽  
Spatial Variations ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Nonradiative Recombination ◽  
Intensity Dependence ◽  
Thermally Activated

ABSTRACTThe temperature dependence of the cathodoluminescence (CL) originating from In0.21Ga0.79As/GaAs multiple quantum wells has been studied between 86 and 250 K. The CL intensity exhibits an Arrenhius-type dependence on temperature (T), characterized by two different activation energies. The spatial variations in activation energy caused by the presence of interfacial misfit dislocations is examined. The CL intensity dependence on temperature for T ≲ 150 K is controlled by thermally activated nonradiative recombination. For T ≳ 150 K the decrease in CL intensity is largely influenced by thermal re-emission of carriers out of the quantum wells.

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.

Mössbauer effect study on the mixed valence state of iron in tourmaline

1988 ◽  
Vol 52 (365) ◽  
pp. 221-228 ◽  
Author(s):  
E. A. Ferrow ◽  
H. Annersten ◽  
R. P. Gunawardane
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Valence State ◽  
Mixed Valence ◽  
Effect Study ◽  
High Activation ◽  
Charge Delocalization ◽  
Thermally Activated ◽  
Different Temperatures ◽  
Iron Bearing

AbstractMössbauer spectra of iron-bearing tourmaline, obtained at different temperatures, show the existence of thermally-activated charge delocalization among clusters of iron atoms situated in the Y and Z octahedra of the tourmaline structure. The temperature dependence indicates an unusually high activation energy for the delocalization process which suggests that the process takes place between crystallographically non-equivalent sites. Annealing of the tourmaline in hydrogen is observed to inhibit the delocalization process, thus localizing the electron into the Z-site.

The Meyer-Neldel Rule in Conductivity of Microcrystalline Silicon

2002 ◽  
Vol 715 ◽  
Author(s):  
Sanjay K. Ram ◽  
Satyendra Kumar ◽  
P. Rocai Cabarrocas
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Film Thickness ◽  
Fermi Level ◽  
Carrier Transport ◽  
Dark Conductivity ◽  
Localized States ◽  
Microcrystalline Silicon ◽  
Thermally Activated ◽  
Density Of Localized States

AbstractThe dark conductivity (σd) has been measured from 300 to 440K on undoped hydrogenated microcrystalline silicon (μc-Si:H) films having different thicknesses. The carrier transport is found to be thermally activated with single activation energy (Ea) in all the samples. The Ea increases as the film thickness decreases. At the same time logarithmic of dark conductivity prefactor (σo) is found to follow a linear relation with activation energy, known as the Meyer-Neldel rule (MNR). Results are explained in terms of increased degree of disorder in thinner samples. Thus change in Ea with the film thickness is directly related to the density of localized states at the Fermi level in grain boundary (GB). Therefore varying the film thickness and, hence, the exponential density of states induces a statistical shift of Fermi level which gives rise to the observed MNR.

Hopping transport in doped co-deposited mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

2011 ◽  
Vol 1321 ◽  
Author(s):  
L. R. Wienkes ◽  
C. Blackwell ◽  
J. Kakalios
Keyword(s):  
Temperature Dependence ◽  
Electronic Transport ◽  
Nanocrystalline Silicon ◽  
Dark Conductivity ◽  
Mixed Phase ◽  
Dependence Analysis ◽  
Thermally Activated ◽  
Silicon Thin Films ◽  
And Shifts ◽  
Hydrogenated Amorphous

ABSTRACTStudies of the electronic transport properties of n-type doped hydrogenated amorphous/nanocrystalline silicon (a/nc-Si:H) films deposited in a dual-plasma co-deposition reactor are described. For these doped a/nc-Si:H, the conductivity increases monotonically for increasing crystal fractions up to 60% and displays marked deviations from a simple thermally activated temperature dependence. Analysis of the temperature dependence of the activation energy for these films finds that the dark conductivity is best described by a power-law temperature dependence, σ = σo (T/To)n where n = 1 – 4, suggesting multiphonon hopping as the main transport mechanism. These results suggest that electronic transport in mixed-phase films occurs through the a-Si:H matrix at lower nanocrystal concentrations and shifts to hopping conduction between clusters of nanocrystals at higher nanocrystal densities.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

Electric-field and temperature dependence of the activation energy associated with gate induced drain leakage

2013 ◽  
Vol 113 (4) ◽  
pp. 044513 ◽  
Author(s):  
Aaesha Alnuaimi ◽  
Ammar Nayfeh ◽  
Victor Koldyaev
Keyword(s):  
Activation Energy ◽  
Electric Field ◽  
Temperature Dependence
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