Hot-Wire CVD Poly-Silicon Films for Thin Film Devices

1998 ◽  
Vol 507 ◽  
Author(s):  
J.K. Rath ◽  
F.D. Tichelaar ◽  
H. Meiling ◽  
R.E.I. Schropp
Keyword(s):  
Defect Density ◽  
Initial Growth ◽  
Oriented Growth ◽  
Compact Structure ◽  
High Hydrogen ◽  
New Approach ◽  
Intrinsic Nature ◽  
Bias Stress ◽  
Hydrogen Dilution ◽  
Long Duration

ABSTRACTSolar cell using profiled poly-Si:H by HWCVD as i-layer in the configuration SS/n-µSi:H(PECVD)/i-poly-Si:H(HWCVD)/p-µc-Si:H(PECVD)/ITO showed 3.7% efficiency. A current of 23.6 mA/cm2 was generated in only 1.5 µm thick poly-Si:H i-layer grown at ∼5Å/s. TFTs made with the poly-Si:H films (grown at ≥ 9Å/s) exhibited remarkable stability to long duration of 23 hours of gate bias stress of ∼lMV/cm. A saturation mobility of 1.5 cm2/Vs for the TFT has been achieved. Films made at low hydrogen dilution (Poly2) showed device quality (purely intrinsic nature, ambipolar diffusion length of 568 nm, only (220) oriented growth and low ESR defect density of <1017/cm3with complete absence of signal due to conduction electrons) but with an incubation phase of amorphous initial growth, whereas the films made at high hydrogen dilution (Polyl) had a polycrystalline initial growth, though with higher defect density, incorporated oxygen and randomly oriented grains. Poly2 films are compact and hydrogen bonding is at compact Si-H sites manifested as 2000 cm−1IR vibration and high temperature hydrogen evolution peak. Exchange interaction of spins and spin pairing are observed while increasing defects in such a compact structure. A new approach has been used to integrate these two regimes of growth to make profiled poly-Si:H layers. The new layers show good electronic properties as well as complete elimination of incubation phase.

Microstructural Defects of Device Quality Hot-Wire Cvd Poly-Silicon Films

1999 ◽  
Vol 557 ◽  
Author(s):  
J.K. Rath ◽  
F.D. Tichelaar ◽  
R.E.I. Schropp
Keyword(s):  
Volume Fraction ◽  
Nucleation Density ◽  
Hot Wire ◽  
Compact Structure ◽  
High Oxygen Content ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Si Films ◽  
Spherical Voids ◽  
Steel Substrates

AbstractTwo types of poly-Si:H thin films made by Hot Wire CVD have been evaluated with respect to utilisation in solar cells. Poly-Si:H films made at high hydrogen dilution are highly porous and have large interconnected voids. The void density is 25000/μm-3 as determined by XTEM. On the other hand, poly-Si:H layers made at low hydrogen dilution have a compact structure and a much smaller density of voids. In these films, two types of voids exist: globular voids smaller than 15 nm, and elongated voids, often located between columns of large crystals of 150-250 nm wide at the top. The density for the 5 - 15 nm spherical voids is usually -50/μm3, but larger concentrations often occur locally, up to 1000/pm3, i.e., 0.05% volume fraction. High oxygen content in the poly-Si films made at high hydrogen dilution is largely due to post deposition intrusion of water vapour through the interconnected voids. Profiled layers are made by depositing device quality poly-Si:H layers (low hydrogen dilution) on top of a seed layer (high hydrogen dilution) of high nucleation density. Cells incorporating profiled poly-Si:H films as i-layers at a deposition rate of 0.5 nm/s were made on stainless steel substrates in the configuration SS/n-μc-Si:H(PECVD)/i-poly-Si:H(HWCVD)/p-μc-Si:H(PECVD)/ITO. For our n-i-p solar cell with poly-Si i-layer we obtained an efficiency of 4.41% and a FF of 0.607. Due to native surface texture a current density of 19.95 mA/cm2 is generated in only ~1.22 μm thick i-layer without back reflector.

Growth and Electronic Properties in Hot Wire Deposited Nanocrystalline Si Solar Cells

2007 ◽  
Vol 989 ◽  
Author(s):  
Kamal Muthukrishnan ◽  
Vikram Dalal ◽  
Max Noack
Keyword(s):  
Electronic Properties ◽  
Defect Density ◽  
Grain Structure ◽  
Degree Of Crystallinity ◽  
Hot Wire ◽  
High Hydrogen ◽  
Filament Temperature ◽  
Random Nucleation ◽  
Hydrogen Dilution ◽  
High Filament

AbstractWe report on the growth and properties of nanocrystalline Si:H grown using a remote hot wire deposition system. Unlike previous results, the temperature of the substrate is not significantly affected by the hot filament in our system. The crystallinity of the growing film and the type of grain structure was systematically varied by changing the filament temperature and the degree of hydrogen dilution. It was found that high hydrogen dilution gave rise to random nucleation and <111> grain growth, whereas lower hydrogen dilution led to preferable growth of <220> grains. Similarly, a high filament temperature gave rise to preferential <111> growth compared to lower filament temperature. The electronic properties such as defect density and minority carrier diffusion length were studied as a function of the degree of crystallinity. It was found that the lowest defect density was obtained for a material which had an intermediate range of crystallnity, as determined from the Raman spectrum. Both highly amorphous and highly crystalline materials gave higher defect densities. The diffusion lengths were measured using a quantum efficiency technique, and were found to be the highest for the mid-range crystalline material. The results suggest that having an amorphous tissue surrounding the crystalline grain helps in passivating the grain boundaries.

Electronic and Structural Characterization of the Near Surface Layer and the Bulk in νc-Si:H Prepared with Hydrogen dilution

1989 ◽  
Vol 164 ◽  
Author(s):  
Samer Aljishi ◽  
Shu Jin ◽  
Martin Stutzmann ◽  
Lothar Ley
Keyword(s):  
Hydrogen Bonding ◽  
Surface Layer ◽  
Optical Absorption ◽  
Structural Characterization ◽  
Defect Density ◽  
Total Yield ◽  
High Hydrogen ◽  
Near Surface ◽  
Hydrogen Dilution

AbstractThe near surface layer and the bulk of νc-Si:H prepared with hydrogen dilution are investigated by Raman, optical absorption, and total yield photoelectron spectroscopies. The results show that for low hydrogen dilution ratios, microcrystallites appear in the bulk while the growing surface layer remains amorphous, indicating that microcrystallite formation takes place primarily in the sub-surface layer. At high hydrogen dilution ratios, microcrystallites are detected at both the bulk and the near surface layer. The defect density and hydrogen bonding configurations at various hydrogen dilution levels are presented.

Material Basis of Highly Stable a-Si:H Solar Cells

1996 ◽  
Vol 420 ◽  
Author(s):  
B. Rech ◽  
S. Wieder ◽  
F. Siebke ◽  
C. Beneking ◽  
H. Wagner
Keyword(s):  
Defect Density ◽  
Short Circuit ◽  
Short Circuit Current ◽  
High Hydrogen ◽  
Interface Recombination ◽  
Hydrogen Dilution ◽  
Process Gas ◽  
Current Densities ◽  
Comprehensive Characterization

AbstractWe achieved a stabilized efficiency of 9.2 % after only 8 % relative degradation for an a-Si:H/a-Si:H stacked cell with the top-cell i-layer prepared at 140 °C using a high hydrogen dilution of the silane process gas. From a comprehensive characterization of p-i-n cells and the corresponding i-layer material prepared at 140 °C and 190 °C substrate temperature with different hydrogen dilutions, we conclude that the performance of these pin cells strongly correlates with the material properties of the corresponding i-layers. High fill factors after light soaking are reflected in a good microstructure, high photo-conductivity, and relatively low defect density. Whereas the initial Voc is limited by interface recombination, volume recombination dominates the forward-dark current after light soaking. The stabilized Voc as well as the short-circuit current densities correlate with the optical bandgap of the i-layer.

Structural and Electronic Properties of Hydrogenated Nanocrystalline Silicon Films Made with Hydrogen Dilution Profiling Technique

2005 ◽  
Vol 862 ◽  
Author(s):  
Keda Wang ◽  
Daxing Han ◽  
D. L. Williamson ◽  
Brittany Huie ◽  
J. R. Weinberg-Wolf ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Growth Direction ◽  
Structure Evolution ◽  
Excitation Wavelength ◽  
Initial Growth ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Structural And Electronic Properties

AbstractWe used X-ray diffraction (XRD), Raman scattering and photoluminescence (PL) spectroscopy to characterize structural and electronic properties of nc-Si:H films made with different hydrogen dilution ratios and hydrogen dilution profiling with continuously reduced hydrogen dilution during the deposition. The XRD results show that the crystalline volume fraction (fc) is in the range of 60-70% with grain size of 22-26 nm for the nc-Si:H films studied. Comparing the sample made using hydrogen dilution profiling to that with constant hydrogen dilution, the hydrogen dilution profiling promotes the (220) preferential orientation due to a very high hydrogen dilution in the initial growth. The Raman results show that the fc is in the range of 60-90%, depending on the sample and excitation wavelength. For the samples with constant hydrogen dilution, the fc measured by Raman increases along the growth direction. The hydrogen dilution profiling reverses this trend, which affirms that the hydrogen profiling controls the nanocrystalline structure evolution along the growth direction. The PL results show only one peak around 0.8-0.9 eV for the samples made with constant hydrogen dilution, but an additional peak at 1.4 eV appears in the sample made with the hydrogen dilution profiling.

CHANGES IN BLOOD PROTEOME OF COSMONAUTS WITH MICRO- AND MACROVASCULAR INJURIES DUE TO G-LOADS AT THE FINAL STAGE OF LONG-DURATION SPACE MISSIONS

2020 ◽  
Vol 54 (5) ◽  
pp. 5-14
Author(s):  
L.Kh. Pastushkova ◽  
◽  
K.S. Kireev ◽  
I.M. Larina ◽  
◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Soft Tissues ◽  
Blood Rheology ◽  
Landing Site ◽  
Space Missions ◽  
Vascular Injuries ◽  
New Approach ◽  
Long Duration ◽  
Integrated Response

The integrated response of the human proteome to re-entry g-loads following long-term space missions was studied in 13 male cosmonauts at the age of 44 ± 6 years. Examination at the landing site discovered local petechial hemorrhages into soft tissues of the back and lower legs. The paper presents a new approach to evaluation of petechia and soft tissue hemorrhages in cosmonauts on return to Earth. Proteomic analysis was performed with the use of LC-MS. Bioinformation analysis was made using Perseus, PubMed, Uniprot and ANDSystem software. Nine out of 19 significantly different (p < 0.05) proteins were related to vascular injuries directly. We described proteins with a primarily protecting effect against endothelial cells apoptosis and augmentation of vascular permeability, proteins that are responsible for blood rheology and proteins antagonistic to the main triggers of ischeamia-reperfusion injuries of the lungs, liver and other parenchymal organs.

Intrinsic and Doped m c-Si:H TFT Layers using 13.56 MHz PECVD at 250°C

2004 ◽  
Vol 808 ◽  
Author(s):  
Czang-Ho Lee ◽  
Denis Striakhilev ◽  
Arokia Nathan
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Rf Power ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Bias Stress ◽  
Hydrogen Dilution ◽  
Low Threshold

ABSTRACTUndoped and n+ hydrogenated microcrystalline silicon (μc-Si:H) films for thin film transistors (TFTs) were deposited at a temperature of 250°C with 99 ∼ 99.6 % hydrogen dilution of silane by standard 13.56 MHz plasma enhanced chemical vapor deposition (PECVD). High crystallinity m c-Si:H films were achieved at 99.6 % hydrogen dilution and at low rf power. An undoped 80 nm thick m c-Si:H film showed a dark conductivity of the order of 10−7 S/cm, the photosensitivity of an order of 102, and a crystalline volume fraction of 80 %. However, a 60 nm thick n+ μc-Si:H film deposited using a seed layer showed a high dark conductivity of 35 S/cm and a crystalline volume fraction of 60 %. Using n+ μc-Si:H films as drain and source contact layers in a-Si:H TFTs provides substantial performance improvement over n+ a-Si:H contacts. Finally, fully μ c-Si:H TFTs incorporating intrinsic m c-Si:H films as channel layers and n+ μc-Si:H films as contact layers have been fabricated and characterized. These TFTs exhibit a low threshold voltage and a field effect mobility of 0.85 cm2/Vs, and are far more stable under gate bias stress than a-Si:H TFTs.

Anomalous Positive Bias Stress Instability in MoS2 Transistors With High-Hydrogen-Concentration SiO2 Gate Dielectrics

2019 ◽  
Vol 40 (2) ◽  
pp. 232-235 ◽  
Author(s):  
Guanhua Yang ◽  
Xichen Chuai ◽  
Jiebin Niu ◽  
Jiawei Wang ◽  
Xuewen Shi ◽  
...  
Keyword(s):  
Hydrogen Concentration ◽  
Gate Dielectrics ◽  
Positive Bias ◽  
High Hydrogen ◽  
Bias Stress

Development of Stable a-Si/a-SiGe Tandem Solar Cell Submodules Deposited by a Very High Hydrogen Dilution at Low Temperature

1998 ◽  
Vol 507 ◽  
Author(s):  
Masaki Shima ◽  
Masao Isomura ◽  
Eiji Maruyama ◽  
Shingo Okamoto ◽  
Hisao Haku ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Silicon Germanium ◽  
Structural Variations ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Hydrogen Radicals ◽  
Amorphous Silicon Germanium ◽  
Hydrogenated Amorphous ◽  
Very High

ABSTRACTThe world's highest stabilized efficiency of 9.5% (light-soaked and measured by the Japan Quality Assurance Organization (JQA)) for an a-Si/a-SiGe superstrate-type solar cell submodule (area: 1200 cm2) has been achieved. This value was obtained by investigating the effects of very-high hydrogen dilution of up to 54:1 (= H2: SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) deposition at a low substrate temperature (Ts). It was found that deterioration of the film properties of a-SiGe:H when Ts decreases under low hydrogen dilution conditions can be suppressed by the high hydrogen dilution. This finding probably indicates that the energy provided by hydrogen radicals substitutes for the lost energy caused by the decrease in Ts and that sufficient surface reactions can occur. In addition, results from an estimation of the hydrogen and germanium contents of a-SiGe:H suggest the occurrence of some kinds of structural variations by the high hydrogen dilution. A guideline for optimization of a-SiGe:H films for solar cells can be presented on the basis of the experimental results. The possibility of a-SiGe:H as a narrow gap material for a-Si stacked solar cells in contrast with microcrystalline silicon (μ c-Si:H) will also be discussed from various standpoints. At present, a-SiGe:H is considered to have an advantage over μ1 c-Si:H.

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