Increase of temperature and crystallinity during electrical switching in microcrystalline silicon

2004 ◽  
Vol 808 ◽  
Author(s):  
Jian Hu ◽  
Paul Stradins ◽  
Howard M. Branz ◽  
Qi Wang ◽  
J.R. Weinberg-Wolf ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Microcrystalline Silicon ◽  
Electrical Measurements ◽  
Current Ramp ◽  
Device Resistance ◽  
Boron Doped ◽  
Current Stressing ◽  
Surface Reflectivity ◽  
Si Films ◽  
A Current

ABSTRACTWe investigate electrical stressing and switching in hydrogenated microcrystalline silicon (mc-Si:H) by thermal, and optical and electrical measurements of Cr/mc-Si:H/metal thin-film structures. Boron-doped microcrystalline Si films of 30-50 nm thick are deposited by hot-wire chemical vapor deposition (HWCVD) on Cr-coated glass at 160°C and contacted with Ag or Al. Switching in devices of size 5 to 30 mm is stimulated by a current-ramp from 10 nA to 50 mA. We find that the voltage across the mc-Si:H devices initially increases logarithmically with current, then saturates at 2∼3 V, and finally drops to a low value of 1 to 1.5 V. This drop indicates a permanent decrease of device resistance to below 1 kW. During current stressing, the surface temperature increases with the bias current, and the surface reflectivity changes. After switching, a small increase in crystalline fraction can be observed by micro-Raman scattering measurements. The observations suggest electrothermal processes which cause changes in microstructure of the mc-Si bulk during current stress.

DEVELOPMENT OF HIGHLY CONDUCTIVE BORON-DOPED MICROCRYSTALLINE SILICON FILMS FOR APPLICATION IN SOLAR CELLS

2006 ◽  
Vol 20 (03) ◽  
pp. 303-314 ◽  
Author(s):  
QING-SONG LEI ◽  
ZHI-MENG WU ◽  
JIAN-PING XI ◽  
XIN-HUA GENG ◽  
YING ZHAO ◽  
...  
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Silicon Films ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Boron Doped ◽  
Deposition Processes ◽  
P Type

We have examined the deposition of highly conductive boron-doped microcrystalline silicon (μc- Si:H ) films for application in solar cells. Depositions were conducted in a very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) chamber. In the deposition processes, various substrate temperatures (TS) were applied. Highly conductive p-type microcrystalline silicon films were obtained at substrate temperature lower than 210°C. The factors that affect the conductivity of the films were investigated. Results suggest that the dark conductivity, which was determined by the Hall mobility and carrier concentration, is influenced by the structure. The properties of the films are strongly dependent on the substrate temperature. With TS increasing, the dark conductivity (σd) increases initially; reach the maximum values at certain TS and then decrease. Also, we applied the boron-doped μc- Si:H as p-layers to the solar cells. An efficiency of about 8.5% for a solar cell with μc- Si:H p-layer was obtained.

Deposition of Amorphous and Microcrystalline Si,C Alloy Thin Films by a Remote Plasma-Enhanced Chemical-Vapor Deposition Process

1991 ◽  
Vol 219 ◽  
Author(s):  
C. Wang ◽  
G. Lucovsky ◽  
R. J. Nemanich
Keyword(s):  
Raman Spectra ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Degree Of Crystallinity ◽  
Microcrystalline Silicon ◽  
Electrical And Optical Properties ◽  
Silicon Carbon ◽  
Infrared Measurements ◽  
Si Films ◽  
The Degree Of Crystallinity

ABSTRACTWe have extended the remote PECVD process to the deposition of intrinsic and doped, amorphous and microcrystalline silicon, carbon alloy films, a-Si,C:H and μc-Si,C, respectively. The electrical and optical properties of a-Si,C:H deposited by remote PECVD are comparable to those of films deposited by the glow discharge or GD process. The degree of crystallinity in the μc-Si,C alloys, as determined from the relative intensities of crystalline and amorphous features in the Raman spectra, is lower than that of μc-Si films deposited under comparable deposition conditions. The Raman spectra indicate that the crystallites in the μc-Si,C alloys are Si, while the infrared measurements establish that the intervening amorphous component is an a-Si,C:H alloy.

Piezoresistive Properties of Boron-Doped PECVD Microcrystalline Silicon Films

1987 ◽  
Vol 106 ◽  
Author(s):  
Shu Wen Guo ◽  
Song Sheng Tan ◽  
Wei Yuan Wang
Keyword(s):  
Thermionic Emission ◽  
State Density ◽  
Gauge Factor ◽  
Optimized Design ◽  
Microcrystalline Silicon ◽  
Boron Doped ◽  
Hole Band ◽  
Si Films ◽  
P Type ◽  
Quartz Substrates

ABSTRACTThe piezoresistive properties of boron-doped PECVD microcrystalline Si films (μc-Si) deposited on SiO2 coated Si, covar or quartz substrates have been investigated. The relations between the gauge factor (G.F.) and doping concentrations as well as the film thickness etc. have been obtained experimentally. The maximum longitudinal G.F. of 25 and 20 are measured for Si and covar substrates respectively. An expression for calculating G.F. of P-type μc-Si is derived theoretically by use of the splitting model of heavy and light hole band at k=0 and the thermionic emission theory. The calculated dependences of G.F. on the doping concentrations, grain size and trap state density agree well with the experimental results, which offer a better understanding of the piezoresistive characteristics of μc-Si or poly-Si, and enable optimized design and fabrication of μc-Si or poly-Si strain gauges.

EFFECTS OF INTERELECTRODE SPACING ON THE PROPERTIES OF MICROCRYSTALLINE SILICON ABSORBER AND SOLAR CELLS

2012 ◽  
Vol 1426 ◽  
pp. 105-110
Author(s):  
Bill Nemeth ◽  
Xiaodan Zhang ◽  
Yanfa Yan ◽  
Qi Wang
Keyword(s):  
Solar Cells ◽  
Growth Parameters ◽  
Short Circuit ◽  
Chemical Vapor ◽  
Short Circuit Current ◽  
Precursor Chemistry ◽  
Short Circuit Current Density ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Si Films

ABSTRACTWe study the effect of the spacing between electrodes in very high frequency plasma enhanced chemical vapor deposition on the properties of microcrystalline silicon films and their related n-i-psolar cells. We vary the spacing from 0.2 to 1.0 cm to deposit microcrystalline silicon at 67.8 MHz while maintaining other growth parameters. The spacing between the electrodes significantly changes the plasma conditions, which govern film precursor chemistry as well as introduce etching and ion bombardment to the film; thereby, influencing nucleation and growth of the microcrystalline Si films. The resulting films were characterized by UV-Vis spectrometry, atomic force microscopy, X-ray diffraction, and transmission electron microscopy. We found that deposition rate decreases, while surface roughness and short circuit current density increase with smaller spacing.

Optical Properties and Structure of Microcrystalline Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
Hien V. Nguyen ◽  
Ilsin An ◽  
Youming Li ◽  
C.R. Wronski ◽  
R.W. Collins
Keyword(s):  
Optical Properties ◽  
Vapor Deposition ◽  
Geometric Model ◽  
Chemical Vapor ◽  
Mean Free Path ◽  
Microcrystalline Silicon ◽  
Dominant Effect ◽  
Si Films ◽  
Electron Mean Free Path ◽  
Classical Size

ABSTRACTThe 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 regime as isolated crystalline particles increase in size. A simple geometric model of nucleation allows us to remove the dominant effect of voids and extract the dielectric functions of the crystallites themselves. We find that the results can be understood in terms of a classical size effect whereby limitations on the electron mean free path by scattering at crystallite surfaces control the absorption onset from 2.0 to 3.0 eV. Finally, we describe how well-ordered, continuous 15 Å c-Si films can be prepared on metal substrates.

In situ Chemical Vapor Deposition of Silicon

1974 ◽  
Vol 32 ◽  
pp. 488-489
Author(s):  
J. L. Kenty
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Metal Films ◽  
Cross Sectional ◽  
Environmental Cell ◽  
Si Films ◽  
A Current

An AEI EM6 electron microscope was modified for the in situ chemical vapor deposition (CVD) of Si films by pyrolysis of SiH4 gas. The environmental cell was so constructed that 100 μm dia. apertures placed 1.6 mm apart formed the top and bottom of the CVD microchamber and permitted a gas flow of up to 0.4 cm3 (STP)/min at up to 10 torr. A current of 2 amps through a single 200 mesh Ti grid of 0.003 mm2 net cross sectional area is sufficient to heat the sample to ~1200°C. Some temperature-heater power calibration experiments were performed by observing the melting point of evaporated metal films.

Influence of Power on the Microstructure and Optical Properties of Microcrystalline Si Films

2014 ◽  
Vol 1016 ◽  
pp. 305-308
Author(s):  
Hua Cheng ◽  
Feng Jiang ◽  
Chang Zheng Ma ◽  
Kuo Jiang
Keyword(s):  
Optical Properties ◽  
Vapor Deposition ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Gaseous Mixture ◽  
Chemical Vapor ◽  
Silicon Films ◽  
Microcrystalline Silicon ◽  
Si Films ◽  
Resonance Plasma

Microcrystalline silicon films were deposited using Ar diluted SiH4 gaseous mixture by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). The effects of power on microstrcture and optical properties of microcrystalline silicon films were investigated. The results show that, with the increasing of the power, the crystallinity increased, but the concentration of hydrogen decreased monotonously. Furthermore, the absorption coefficient of the films increased monotonously, and the optical bandgap changed from 1.89eV to 1.75eV with the microwave power ranging from 400 W to 650W.

Boron Doping Effects in Microcrystalline Silicon

2007 ◽  
Vol 989 ◽  
Author(s):  
Wolfhard Beyer ◽  
Lars Niessen ◽  
Frank Pennartz
Keyword(s):  
Doping Level ◽  
Amorphous Material ◽  
Boron Doping ◽  
Crystalline Material ◽  
Microcrystalline Silicon ◽  
High Concentration ◽  
Compact Structure ◽  
Boron Doped ◽  
Doping Effects ◽  
Si Films

AbstractConditions leading to high conductivities (up to 300 S/cm) in chlorosilane-based boron-doped microcrystalline Si:Cl:H films are investigated. It is found that the high conductivity originates primarily from the growth of highly crystalline material with a high concentration of boron. Furthermore, these films grow with relatively low chlorine and hydrogen concentrations of a few percent and, according to effusion measurements of hydrogen and implanted helium, in a relatively compact structure. At a boron doping level of 1%, admixture of 10% silane to the tetrachlorosilane results in the growth of amorphous material of low conductivity while for admixture of up to 90% of silicontetrafluoride, microcrystalline Si films with high conductivities can be grown.

High Quality Microcrystalline Silicon-Carbide Films Prepared by Photo-CVD Method Using Ethylene Gas as a Carbon Source

1999 ◽  
Vol 557 ◽  
Author(s):  
Seung Yeop Myong ◽  
Hyung Kew Lee ◽  
Euisik Yoon ◽  
Koeng Su Lim
Keyword(s):  
Silicon Carbide ◽  
Vapor Deposition ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Microcrystalline Silicon ◽  
Cvd Method ◽  
Hydrogen Dilution ◽  
Boron Doped

AbstractHydrogenated boron-doped microcrystalline silicon-carbide (p-μc-SiC:H) films were grown by a photo chemical vapor deposition (photo-CVD) method from silane (SiH4), hydrogen (H2), diborane (B2H6), and ethylene (C2H4) gases. Since the photo-CVD is a mild process (~10mW/cm2), we can avoid the ion damage of the film, which is inevitable during the deposition of μc-SiC:H employing conventional PECVD technique. A dark conductivity as high as 5 × 10-1 S/cm, together with an optical bandgap of 2 eV, was obtained by the C2H4 addition, which is the first approach in photo-CVD systems. From the Raman and FTIR spectra, it is clear that our p-μc-SiC:H films are made up of crystalline silicon grains embedded in amorphous silicon-carbide tissue. We investigate the role of the hydrogen dilution and ethylene addition on the electrical, optical, and structural properties of p-μc-SiC:H films.

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