Plasma Deposition and Characterization of Stable a-Si:H (Cl) From a Silane-Dichlorosilane Mixture

1995 ◽  
Vol 377 ◽  
Author(s):  
I. S. Osborne ◽  
N. Hata ◽  
A. Matsuda
Keyword(s):  
Defect Density ◽  
Plasma Deposition ◽  
Chemical Vapor ◽  
Mixing Ratio ◽  
Film Properties ◽  
Laser Illumination ◽  
Induced Defects ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon containing chlorine (a-Si:H (Cl)) films have been grown by plasma enhanced chemical vapor deposition from a mixture of silane and dichlorosilane with a dichlorosilane concentration up to 60%. We report on the film properties in the as-deposited state and the behavior of the films under both high intensity pulsed laser illumination and long-term AMI illumination. With increasing dichlorosilane concentration the films show an increased resilience to the creation of light induced defects, as determined from the constant photocurrent method. After 900 hours under AMI illumination, the defect density shows a minimum (< 1016 cnr−3) for a 10 % mixing ratio.

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.

Influence de la température de substrat sur la croissance et les propriétés des films minces de silicium amorphe déposés par pulvérisation cathodique

2003 ◽  
Vol 81 (11) ◽  
pp. 1293-1302
Author(s):  
S Abdesselem ◽  
A Ouhab ◽  
M S Aida
Keyword(s):  
Substrate Temperature ◽  
Film Growth ◽  
Defect Density ◽  
Deposition Method ◽  
Rf Power ◽  
Film Properties ◽  
Visible Absorption ◽  
Knowing That ◽  
Spraying Method

We deposit thin films of a-Si:H by RF diode spray on substrate with temperatures varying from 200 to 500 °C. Knowing that this deposition method is violent when compared with the plasma-assisted deposition method, we have used low RF power to limit the energy of the Ar ions bombarding the surface of the growing film. Characterization of the films by UV–visible absorption spectroscopy suggests that the influence of the substrate temperature can be classified into three different regimes: (i) low temperature, Ts < 300 °C: the films show a strong disorder, the hydrogen is bound only in the polyhydric configuration; (ii) intermediate temperature, 300 °C < Ts < 400 °C: film growth is rapid, the films present a lower defect density; this may be the best regime to make good quality a-Si:H films using the spraying method; (iii) high temperature, Ts > 400 °C: the films are more organized, but less hydrogenated. The substrate temperature influences the film properties by modifying the growing mechanism through a control of the reactions taking place at the plasma–substrate interface, where the hydrogen dynamics play a fundamental role.[Journal translation]

Properties of a-Si:H and a-SiGe:H Films Deposited by Photo-Assisted CVD

1986 ◽  
Vol 70 ◽  
Author(s):  
R. E. Rocheleau ◽  
S. C. Jackson. ◽  
S. S. Hegedus ◽  
B. N. Baron
Keyword(s):  
High Efficiency ◽  
Chemical Vapor ◽  
Photovoltaic Cell ◽  
Gas Flows ◽  
Long Term Stability ◽  
Improved Stability ◽  
Deposition Processes ◽  
P Type

ABSTRACTChemical vapor deposition techniques, in particular plasma enhanced CVD, have been used to produce high quality a-Si:H materials. Continuing research is directed toward increased device performance, improved stability, and translation of scale to commercial production. A part of this effort is the evaluation of alternate CVD techniques which in addition to providing technical options for high efficiency and long term stability are likely to lead to improved understanding of the relationships between deposition processes and material properties. A relatively new technique for depositing a-Si:H is photo-CVD which utilizes ultraviolet light to initiate the decomposition of silane or disilane. The best results from both materials properties and device efficiency points of view have been achieved using mercury sensitized photo-CVD. Recently, a 10.5% efficient a-Si:H p-i-n photovoltaic cell, fabricated by photo-CVD, was reported [1]. A limitation in photo-CVD has been preventing deposition on the UV transparent window. In this paper we describe a new photo-CVD reactor with a moveable UV-transparent Teflon film and secondary gas flows to eliminate window fouling. The deposition and opto-electronic characterization of intrinsic a-Si:H and a-SiGe:H and p-type a-SiC:H are described. Finally, preliminary results of p-i-n solar cells are presented.

Hydrogenated Amorphous Silicon Alloys Prepared by CVD of Higher Silanes

1986 ◽  
Vol 70 ◽  
Author(s):  
Masud Akhtar ◽  
Herbert A. Weaklie
Keyword(s):  
Amorphous Silicon ◽  
Band Gap ◽  
Plasma Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Wide Band ◽  
Dark Conductivity ◽  
Attractive Alternative ◽  
Silicon Alloys ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon may be deposited at relatively low temperatures, where the density of defects may be expected to be low, by the chemical vapor deposition (CVD) of higher silanes. This method is an attractive alternative to plasma deposition techniques. We describe here the preparation of a-Si:H and related alloys incorporating carbon, germanium, and fluorine. a-Si:H films were deposited on heated substrates in the range 365°C-445°C by CVD of Si2H6 and Si3H8. The optical gap (Eg) ranged from 1.4 to 1.7 eV and the properties of films deposited from either Si2 H6 or Si3 H8 were quite similar. Wide band gap (Eg=2 eV) alloys of a-SiC:H doped with boron were prepared by CVD of disilane, methyl silane, and diborane. We also prepared variable band gap a-SiC:H alloys by substituting F2C= CFH for methylsilane, and these films were found to have approximately 1–2% fluorine incorporated. The dark conductivity of the boron doped a-SiC:H alloys dep~sited from either carbon source ranged from ix10-7 to 6x10-7 (ohm-cm)-1. We also prepared low band aap alloys of Si and Ge by CVD of trisilane and germane. The band gap of a film containing 20% Ge was 1.5 eV; however, the photoconductivity of the film was relatively low.

In Situ Probing and Atomistic Simulation of a-Si:H Plasma Deposition

2001 ◽  
Vol 664 ◽  
Author(s):  
Eray S. Aydil ◽  
Dimitrios Maroudas ◽  
Denise C. Marra ◽  
W. M. M. Kessels ◽  
Sumit Agarwal ◽  
...  
Keyword(s):  
Plasma Deposition ◽  
Atomistic Simulations ◽  
Experimental Measurements ◽  
Supporting Evidence ◽  
Flat Panel Displays ◽  
Film Properties ◽  
Elementary Processes ◽  
Silicon Thin Films ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon thin films deposited from SiH4 containing plasmas are used in solar cells and thin film transistors for flat panel displays. Understanding the fundamental microscopic surface processes that lead to Si deposition and H incorporation is important for controlling the film properties. An in situ method based on attenuated total internal reflection Fourier transform infrared (ATR-FTIR) spectroscopy was developed and used to determine the surface coverage of silicon mono-, di-, and tri-hydrides as a function of deposition temperature and ion bombardment flux. Key reactions that take place on the surface during deposition are hypothesized based on the evolution of the surface hydride composition as a function of temperature and ion flux. In conjunction with the experiments, the growth of a-Si:H on H-terminated Si(001)-(2×1) surfaces was simulated through molecular dynamics. The simulation results were compared with experimental measurements to validate the simulations and to provide supporting evidence for radical-surface interaction mechanisms hypothesized based on the infrared spectroscopy data. Experimental measurements of the surface silicon hydride coverage and atomistic simulations are used synergistically to elucidate elementary processes occurring on the surface during a-Si:H deposition.

Characterization of Amorphous Silicon Thin Films Deposited on Upilex-s Polyimide Substrates for Application in Flexible Solar Cells

2009 ◽  
Vol 87-88 ◽  
pp. 416-421 ◽  
Author(s):  
Ying Ge Li ◽  
Dong Xing Du
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Flexible Electronics ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Conductivity Measurements ◽  
Silicon Thin Films ◽  
Hydrogenated Amorphous

Upilex-s [poly(biphenyl dianhydride-p-phenylene diamine)] polyimide have been widely employed in the area of flexible electronics. For its potential application on fabricating flexible solar cells, the optical properties of Upilex-s are measured in this paper. Intrinsic hydrogenated amorphous silicon layers are then deposited on Upilex-s substrates at temperatures 100°C and 180°C by plasma enhanced chemical vapor deposition (PECVD) system. As an comparison, intrinsic a-Si:H layers are also fabricated on glass substrate of Corning2000. Both layers on flexible and rigid substrates are thoroughly characterized by activation energy and dark conductivity measurements. It can be concluded that the intrinsic layer on Upilex-s has favorable properties and could be a competitive candidate as substrate materials of flexible solar cells.

Electrical characterization of low defect density nonpolar (11¯20) a-plane GaN grown with sidewall lateral epitaxial overgrowth (SLEO)

2008 ◽  
Vol 23 (2) ◽  
pp. 551-555 ◽  
Author(s):  
Bilge Imer ◽  
Benjamin Haskell ◽  
Siddharth Rajan ◽  
Stacia Keller ◽  
Umesh K. Mishra ◽  
...  
Keyword(s):  
Metalorganic Chemical Vapor Deposition ◽  
Defect Density ◽  
Electrical Characterization ◽  
Chemical Vapor ◽  
Extended Defects ◽  
Electrical Characteristics ◽  
Lateral Epitaxial Overgrowth ◽  
High Defect Density ◽  
Si Doped

We studied the effect of extended defects on electrical characteristics of Si doped n-type nonpolar a-plane GaN films. The n-type GaN layers were grown on co-loaded reduced defect density sidewall lateral epitaxial overgrowth (SLEO) a-plane GaN templates and high defect density planar a-plane GaN templates by metalorganic chemical vapor deposition (MOCVD). The highest conductivity value was observed at the carrier concentration of 1.05 × 1019 cm−3 as 261.12 cm2/Vs for SLEO a-GaN and 106.77 cm2/Vs for the planar a-plane GaN samples. At the same doping level, the carrier compensation for SLEO samples was ∼12% less than planar samples.

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