A Defect Density of ∼ 1014 cm-3 in Hydrogenated Amorphous Silicon Deposited at High Substrate Temperatures

1992 ◽  
Vol 258 ◽  
Author(s):  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Deposition Rate ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate ◽  
Surface Mobility ◽  
Surface Hydrogen ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

ABSTRACTThe idea of surface mobility of growth precursors determined material quality has been exploited by raising the substrate temperature above the conventional 250°C and the ensuing thermal depletion of the surface hydrogen coverage compensated by increasing the precursor flux (deposition rate) to prepare ultra low defect density hydrogenated amorphous silicon.

Reduction of the Defect Density in a-Si:H Deposited at ≤250°C

1993 ◽  
Vol 297 ◽  
Author(s):  
Hitoshi Nishio ◽  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Diffusion Coefficient ◽  
Amorphous Silicon ◽  
Surface Diffusion ◽  
Film Growth ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Device Fabrication ◽  
Surface Diffusion Coefficient ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

We present a method to reduce the defect density in hydrogenated amorphous silicon (a-Si:H) deposited at low substrate temperatures similar to those used for device fabrication . Film-growth precursors are energized by a heated mesh to enhance their surface diffusion coefficient and this enables them to saturate more surface dangling bonds.

Effect of Deposition-Induced Annealable Defects on Light-Induced Defect Generation in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Jong-Hwan Yoon
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Generation Rate ◽  
Defect Generation ◽  
Saturated State ◽  
Microscopic Models ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

In this paper we present a method to determine the annealable defect density(ΔNann) present in hydrogenated amorphous silicon(a-Si:H). The effects of the annealable defects on the light-induced defect generation rate, saturated defect density (Nsat) and the change of defect density in the light-induced saturated state(ΔNsat) have been studied. Annealable defect density was varied by depositing samples at various substrate temperatures or by post-growth anneals of samples grown at low substrate temperatures. It is found that the generation rate, N satand ΔNsat are well correlated with ΔNann. In particular, the ΔNsat is found to follow a relation ΔNsat ≈ ΔNann. These results suggest that defect-related microscopic models are appropriate for light-induced metastability.

High Substrate Temperature (420 °C) Excimer Laser Crystallization of Hydrogenated Amorphous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Carluccio ◽  
A. Pecora ◽  
G. Fortunato ◽  
J. Stoemenos ◽  
N. Economou
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Excimer Laser ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate Temperature ◽  
Solidification Velocity ◽  
Laser Crystallization ◽  
Excimer Laser Crystallization ◽  
Hydrogenated Amorphous ◽  
Substrate Temperatures

ABSTRACTExcimer laser crystallization of hydrogenated amorphous silicon has been investigated as a function of substrate temperature. At low substrate temperatures hydrogen out-diffusion strongly influences the film morphology, while at 420 °C homogeneous recrystallized films are obtained, as a result of the reduced solidification velocity. This process has been successfully tested by fabricating with the recrystalllized material thin-film transistors according to the bottom-gate configuration.

Low Hydrogen Content, High Quality Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
Brent P. Nelson ◽  
Richard S. Crandall ◽  
Eugene Iwaniczko ◽  
A. H. Mahan ◽  
Qi Wang ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Defect Density ◽  
Flow Direction ◽  
Scale Up ◽  
Hydrogenated Amorphous Silicon ◽  
Hot Wire ◽  
High Quality ◽  
Hydrogenated Amorphous

AbstractWe grow hydrogenated amorphous silicon (a-Si:H) by Hot-Wire Chemical Vapor Deposition (HWCVD). Our early work with this technique has shown that we can grow a-Si:H that is different from typical a-Si:H materials. Specifically, we demonstrated the ability to grow a-Si:H of exceptional quality with very low hydrogen (H) contents (0.01 to 4 at. %). The deposition chambers in which this early work was done have two limitations: they hold only small-area substrates and they are incompatible with a load-lock. In our efforts to scale up to larger area chambers—that have load-lock compatibility—we encountered difficulty in growing high-quality films that also have a low H content. Substrate temperature has a direct effect on the H content of HWCVD grown a-Si:H. We found that making dramatic changes to the other deposition process parameters—at fixed substrate temperature and filament-to-substrate spacing—did not have much effect on the H content of the resulting films in our new chambers. However, these changes did have profound effects on film quality. We can grow high-quality a-Si:H in the new larger area chambers at 4 at. % H. For example, the lowest known stabilized defect density of a-Si:H is approximately 2 × 1016 cm-3, which we have grown in our new chamber at 18 Å/s. Making changes to our original chamber—making it more like our new reactor—did not increase the hydrogen content at a fixed substrate temperature and filament-to-substrate spacing. We continued to grow high quality films with low H content in spite of these changes. An interesting, and very useful, result of these experiments is that the orientation of the filament with respect to silane flow direction had no influence on film quality or the H content of the films. The condition of the filament is much more important to growing quality films than the geometry of the chamber due to tungsten-silicide formation on the filament.

Hydrogenated amorphous silicon films prepared at high substrate temperature: Properties and light induced degradation

1993 ◽  
Vol 73 (11) ◽  
pp. 7435-7440 ◽  
Author(s):  
Ratnabali Banerjee ◽  
Sukriti Ghosh ◽  
S. Chattopadhyay ◽  
A. K. Bandyopadhyay ◽  
P. Chaudhuri ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
High Substrate Temperature ◽  
Silicon Films ◽  
High Substrate ◽  
Hydrogenated Amorphous

Assessment of Intrinsic-Layer Growth Temperature to High-Deposition-Rate a-Si:H n-i-p Solar Cells Deposited by Hot-Wire CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
Qi Wang ◽  
Eugene Iwaniczko ◽  
Yueqin Xu ◽  
Brent P. Nelson ◽  
A. H. Mahan
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Diffusion Length ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Ambipolar Diffusion ◽  
Hot Wire ◽  
Top Contact ◽  
Hydrogenated Amorphous

AbstractWe report progress in hydrogenated amorphous silicon n-i-p solar cells with the i-layer grown by the hot-wire chemical vapor deposition technique. Early research showed that we grew device-quality materials with low saturated defect density (2 × 106/cm3), high initial ambipolar diffusion length (~2000 Å) and low hydrogen content (<1%). One of the major barriers to implementing this material into solar cells is the high substrate temperature required (>400°C). We re-assess the effects of low substrate temperature on the property of the films and the performance of the solar cells as an alternative avenue to solving this problem. We find that the material grown at 300°C can have similar values of saturated defect density and ambipolar diffusion length as the one grown greater than 400°C. We also study the effect of i-layer substrate temperature ranging from 280° to 440°C for n-i-p solar cells. We now consistently grow devices with Fill Factor (FF) greater than 0.66, with the best close to 0.70 at lower substrate temperature. A collaboration with United Solar System, in where they grew the p-layer and top contact, produced devices with initial efficiencies as high as 9.8%. We produce n-i-p solar cells with initial efficiencies as high as 8% when we grow all the hydrogenated amorphous silicon and top contact layers. All these i-layers are grown at deposition rates of 16 to 18 Å/sec. We need to further improve our p-layer and transparent conductor layer to equal the collaborative cell efficiency. We also report light-soaking results of these devices.

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