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Article
Photocarrier Transport and Recombination in Amorphous Silicon
The effect of microstructure in undoped a-Si:H films on carrier transport, recombination, densities of midgap states and solar cell characteristics has been investigated. Extended state mobilities of electrons...
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Article
Sub-Surface Equilibration of Hydrogen with the a-Si:H Network Under Film Growth Conditions
In this study we characterize hydrogen diffusion and reaction processes in the near-surface (top 200 Å) of a-Si:H that lead to network equilibration under standard conditions of plasma-enhanced chemical vapor ...
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Article
Optoelectronic Properties of Plasma CVD a-Si:H Modified by Filament-Generated Atomic H
We have studied a-Si:H prepared by alternating plasma deposition with atomic H treatments performed with a heated W filament. Real time spectroscopie ellipsometry provides the evolution of film thickness, opti...
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Article
Optical Properties of Hydrogenated Amorphous Silicon, Silicon-Germanium and Silicon-Carbon Thin Films
The optical properties of solar cell grade hydrogenated amorphous silicon (a-Si:H), silicon germanium (a-SiGe:H) and silicon carbon (a-SiC:H) alloy thin films have been investigated over a wide photon energy r...
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Article
Electron Transport Mechanisms in Nickel Schottky Barrier Contacts to Hydrogenated Amorphous Silicon
Dark J-V characteristics of Ni Schottky diodes on a-Si:H films of various thicknesses were measured as a function of device temperature. Room-temperature photoconductivity and sub-bandgap absorption v. wavelen...
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Article
Experimental Determination of the Dark Fermi Level in Hydrogenated Amorphous Silicon.
The position of the dark fermi level in hydrogenated amorphous silicon (a-Si:H) is important in determining its electrical properties and is a key parameter in the detailed modelling of materials and devices. ...
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Article
Modification of a-Si(:H) by Thermally Generated Atomic Hydrogen: A Real Time Spectroscopic Ellipsometry Study of Si Bond Breaking
We have applied real time spectroscopie ellipsometry (2.5≤h≤4.5 eV) to investigate in situ hydrogenation of thin film a-Si:H prepared by plasma-enhanced CVD. When a-Si:H is exposed to atomic H generated by a t...
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Article
Optical Properties and Structure of Microcrystalline Silicon
The optical properties of thin film microcrystalline silicon (μc-Si:H) prepared by plasma-enhanced chemical vapor deposition (PECVD) have been studied by real time spectroscopie ellipsometry in the nucleation ...
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Article
Surface Microstructural Evolution of Ultrathin films by Real time Spectroscopic Elupsometry
Vapor deposition of smooth, microstructurally uniform amorphous films on dissimilar substrates requires coalescence of clusters that form during initial nucleation. We have developed techniques that provide su...
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Article
Charge-Defect Equilibrium Description of the Staebler-Wronski Defect Concentration and Formation Energy
An equilibrium framework for the high temperature behavior of dangling bond defects in amorphous materials is developed. With this framework it is possible to relate the thermal formation of defects directly w...
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Article
Probing the Densities of Gap States in Intrinsic a-Si:H Using Space Charge Limited Currents of Electrons and Holes
Space charge limited currents of holes in intrinsic hydrogenated amorphous silicon (a-Si:H) have been obtained using novel p+-intrinsic-p+ (p-i-p) structures. The presence of these hole space charge limited curre...
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Article
Effects of Interfaces on the a-Si:H Schottky Barrier Characteristics
A detailed study of hydrogenated amorphous silicon (a-Si:H) surfaces during etching and subsequent low temperature (T≤200°C) oxidation was carried out using in-situ and spectroscopic ellipsometry (SE). The micros...
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Article
The Movement of Mobility Edges in Hydrogenated Amorphous Silicon
Internal photoemission of both electrons and holes is used to investigate the movement of the mobility edges in high quality intrinsic, undoped hy-drogenated amorphous silicon (a-Si:H) with temperature and ele...
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Article
Rectification and internal photoemission in metal/CVD diamond and metal/CVD diamond/silicon structures
Schottky diodes were formed with free-standing polycrystalline thin film diamond base as well as with polycrystalline diamond films grown on crystalline silicon. Current-voltage and internal photoemission meas...
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Article
The Internal Photoemission of Electrons and Holes from Metals into Hydrogenated Amorphous Silicon
Internal photoemission is used to investigate the mobility edges in high quality, undoped, hydrogenated amorphous silicon (a-Si:H). The detailed studies carried out on intimate metal/ a- Si:H Schottky barriers...
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Article
Electrical Properties of Homoepitaxial Diamond Films
We describe the electrical characteristics of boron doped homoepitaxial diamond films fabricated using a plasma assisted CVD process, formation of ohmic contacts, high temperature (580°C) Schottky diodes, and ...
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Article
Carrier Transport in Compositionally Modulated a-Si:H Based Superlattice Structures
Results are presented on the electron transport, parallel and perpendicular to the layers, in a Ge:H/a-Si:H superlattices. The dependence of this carrier transport on the optical gap shifts, the heterojunction...
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Article
Optoelectronic Properities of A-Ge:H/A-Si:H Superlattic Structures
The optoelectronic properties of multilayer a-Ge:H/a-Si:H superlattices with bandgaps between ∼ 1.4 and 1.1eV are presented. The dependence of the electronic properties on the band alignment and the layer thic...
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Article
Enhancement of Photocarrier Lifetime Due to Charge Separation in a-Si:H/a-Ge:H Superlattices
The lifetime of photogenerated electrons in a-Ge:H/a-Si:H multilayer structures with layers about 100Å thick, is enhanced by two orders of magnitude above the value in bulk a-Ge:H. This lifetime enhancement ef...
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Article
Reversible, Light Induced Changes in a-Si:H Films and Solar Cells
Continuous progress is being made in the conversion efficiencies of a-Si:H solar cells and efficiencies in excess of 11% have been achieved. Because of these advances and the development of a-Si:H cell technol...
