Optical Degradation and Morphology in a-Si:H

1989 ◽  
Vol 149 ◽  
Author(s):  
Jun-ichi Nakata ◽  
Atsushi Miyanishi ◽  
Junji Shirafuji ◽  
Shozo Imao ◽  
Keiji Fujibayashi ◽  
...  
Keyword(s):  
Activation Energy ◽  
Hydrogen Diffusion ◽  
Hydrogenated Amorphous Silicon ◽  
Electron Trap ◽  
Simultaneous Increase ◽  
Hole Trap ◽  
Dangling Bonds ◽  
Higher Temperature ◽  
The Relationship ◽  
Hydrogenated Amorphous

ABSTRACTThe relationship between the optical degradation and the morphology of hydrogenated amorphous silicon (a-Si:H) films was studied through the analysis of the annealing processes. The annealing of optically induced metastable dangling bonds can be explained in terms of the first and the second order reactions with dispersive hydrogen diffusion for the films deposited at lower and higher temperature, respectively. The activation energy of the annealing was estimated to be 0.8 eV with a small distribution in both cases. Optically enhanced annealing was first observed. It was found by DLTS and CT measurements that the density of hole trap located at Ev+0.6 eV was remarkably decreased by the light soaking, accompanied by the simultaneous increase of electron trap at Ec-0.7 ∼ Ec-0.9 eV due to the dangling bonds. These experimental facts support the view that the hole trap corresponds to the weak bonds, which convert to the metastable dangling bonds by light soaking.

New experiments on the relationship between light-induced defects and photoconductivity degradation

2001 ◽  
Vol 664 ◽  
Author(s):  
Stephan Heck ◽  
Howard M. Branz
Keyword(s):  
Activation Energy ◽  
Defect Density ◽  
Activation Energies ◽  
Dangling Bond ◽  
Fast Recovery ◽  
Slow Recovery ◽  
Degradation Model ◽  
Induced Defects ◽  
The Relationship ◽  
Hydrogenated Amorphous

ABSTRACTWe report experimental results that help settle apparent inconsistencies in earlier work on photoconductivity and light-induced defects in hydrogenated amorphous silicon (a-Si:H) and point toward a new understanding of this subject. After observing that light-induced photoconductivity degradation anneals out at much lower T than the light-induced increase in deep defect density, Han and Fritzsche[1] suggested that two kinds of defects are created during illumination of a-Si:H. In this view, one kind of defect degrades the photoconductivity and the other increases defect sub-bandgap optical absorption. However, the light-induced degradation model of Stutzmann et al.[2] assumes that photoconductivity is inversely proportional to the dangling-bond defect density. We observe two kinds of defects that are distinguished by their annealing activation energies, but because their densities remain in strict linear proportion during their creation, the two kinds of defects cannot be completely independent.In our measurements of photoconductivity and defect absorption (constant photocurrent method) during 25°C light soaking and during a series of isochronal anneals between 25 < T < 190°C, we find that the absorption measured with E ≤1.1 eV, first increases during annealing, then exhibits the usual absorption decrease found for deeper defects. The maximum in this absorption at E ≤1.1eV occurs simultaneously with a transition from fast to slow recovery of photoconductivity. The absorption for E ≤1.1eV shows two distinct annealing activation energies: the signal rises with about 0.87 eV and falls with about 1.15 eV. The 0.87 eV activation energy roughly equals the activation energy for the dominant, fast, recovery of photoconductivity. The 1.15 eV activation energy roughly equals the single activation energy for annealing of the light-induced dangling bond absorption.

Role of Hydrogen Microstructure in Amorphous Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
Sufi Zafar ◽  
E. A. Schiff
Keyword(s):  
Amorphous Silicon ◽  
Hydrogen Evolution ◽  
Hydrogen Diffusion ◽  
Hydrogenated Amorphous Silicon ◽  
Hydrogenated Amorphous ◽  
Unified Description

ABSTRACTA model for correlating the observed properties of hydrogenated amorphous silicon (a-Si:H) with the underlying hydrogen microstructure is reviewed. The model provides a unified description of defect equilibration, hydrogen evolution, rehydrogenation and hydrogen diffusion measurements.

Hydrogenated Amorphous Silicon Films Prepared by Mercury Sensitized Photochemical Vapor Deposition

1989 ◽  
Vol 149 ◽  
Author(s):  
Takaaki Kamimura ◽  
Hidetoshi Nozaki ◽  
Naoshi Sakuma ◽  
Mitsuo Nakajima ◽  
Hiroshi Ito
Keyword(s):  
Amorphous Silicon ◽  
Deposition Rate ◽  
Hydrogenated Amorphous Silicon ◽  
Gas Phase Reactions ◽  
Bond Density ◽  
Hydrogen Elimination ◽  
Photochemical Vapor Deposition ◽  
The Relationship ◽  
Hydrogenated Amorphous ◽  
Activation Type

ABSTRACTHydrogenated amorphous silicon (a-Si:H) films were prepared by mercury photosensitized decomposition of silane using a low-pressure mercury lamp. The deposition rate showed an activation type for substrate temperature (the activation energy: 0.13 eV), because the deposition rate would be determined by the rate of hydrogen elimination from the hydrogen saturated surface. Moreover, the relationship was found between the Si-H2 bond density in a- Si:H films and the gas phase reactions.

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