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Methods of growing heterepitaxial single crystal or large grained semiconductor films and devices thereon

a technology of semiconductor films and superconducting films, which is applied in the direction of sustainable manufacturing/processing, ways, instruments, etc., can solve the problems of significant drop in photovoltaic technology cost, major cost component of photovoltaic cells is the cost of the substrate on which the semiconductor is mounted, and achieve the effect of facilitating the growth of epitaxial superconducting films

Inactive Publication Date: 2009-12-03
SOLAR TECTIC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention provides a method for producing high-quality semiconductor films, particularly silicon films, for photovoltaic technology and other semiconductor devices. The method involves alloying semiconductor with elements or compounds that form an eutectic system and increasing the concentration of semiconductor through a liquidus line to nucleate out of the melt on a substrate. The resulting films are of low temperature, can be produced on inexpensive substrates, and have a highly textured surface. The method is less expensive than existing methods and can be used for the production of materials suitable for photovoltaic technologies."

Problems solved by technology

A dominant factor in favor of the continual use of fossil fuels is their cost per unit of available energy.
A major cost component in photovoltaic cells is the cost of the substrate on which the semiconductor film capable of converting sunlight into electricity is placed.
If a silicon film could be deposited on an inexpensive substrate, such as glass, and with comparable quality as that found in silicon single crystals used in the microelectronics industry, the cost of photovoltaic technology would drop significantly.
In contrast to metals, semiconductors, such as silicon, are difficult to grow epitaxially.
A disadvantage in this approach is the eutectic temperature, which is generally high.
While this is an advantage, there is also a serious disadvantage; at these low temperatures, the silicon film can contain defects and hence are not very useful as a photovoltaic material.
However it is not high enough to use conventional deposition temperature of greater than 750 degrees Centigrade for silicon on insulator, such as a sapphire substrate.
One limitation of the use of glass as a substrate has been its softening temperature, which is generally lower than the conventional processing temperatures required for the growth of large grained or single crystal films of silicon.

Method used

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  • Methods of growing heterepitaxial single crystal or large grained semiconductor films and devices thereon
  • Methods of growing heterepitaxial single crystal or large grained semiconductor films and devices thereon

Examples

Experimental program
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example 1

[0050]A good high vacuum system with two electron beam guns, is used to deposit gold and silicon independently. A glass substrate coated with ion beam assisted deposited MgO film is held at temperatures between 575 and 600° C. These are nominal temperatures. It is understood to one skilled in the art that lower or higher temperatures can also be used depending upon the softening temperature of the glass substrate or the reaction kinetics of either gold or silicon with the metallic tape or its buffer layers when used a substrates. A thin gold film of approximately 10 nm thickness is deposited first. This is followed by a silicon film deposited at a rate of 2 nm per minute on top of the gold film. The ratio of the thickness of the gold and silicon films is chosen such that the final composition ensures that a point, marked 14, in FIG. 1 is reached. This point lies in the two phase region of solid Si and a liquid Si—Au mixture. For example, for a 10 nm gold film followed a 100 nm silic...

example 2

[0055]A good high vacuum system with two electron beam guns is used to deposit aluminum and silicon independently. A glass substrate or a Ni based substrate coated with a buffer layer of Al2O3 is held at temperatures between 600 and 615° C. These are nominal temperatures. It is understood to one skilled in the art that lower or higher temperatures can also be used depending upon the softening temperature of the glass substrate or the reaction kinetics of either aluminum or silicon with the metallic tape or its buffer layers when used a substrates. The eutectic Al—Si is used instead of the Au—Si example above. A thin Al film 6 nm thick is deposited on the Al2O3 followed by a 100 nm thick silicon deposition, and as described in example 1, above, the two phase region comprising of solid silicon and a liquid Si—Al mixture is reached. The deposition is stopped and the sample is slowly cooled to room temperature. Aluminum diffuses through the silicon film, driven by its lower surface ener...

example 3

[0057]We describe in this example how different methods of deposition can be combined to take advantage of highly textured films as described in example 1, above. The Si film produced from the deposition of example 1 is etched to remove the Au and then placed back into the vacuum chamber and p+-Si is deposited on this film. This latter layer serves two purposes: it provides a conducting layer for a photovoltaic device to be subsequently built on it and can be the starting point for a variety of differently configured photovoltaic devices as, for example, a nanowire photovoltaic device. Here a 2-3 nm thick gold film is deposited on the silicon using an electron gun. This 2-3 nm thick gold film breaks up into nanoparticles and is the starting point used by a number of investigators to use chemical vapor deposition to grow nanowires and use these nanowires for photovoltaic devices. The difference is that we show how an inexpensive buffered glass can be used rather than a relatively exp...

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Abstract

A method is disclosed for making semiconductor films from a eutectic alloy comprising a metal and a semiconductor, which are vapor deposited at a fixed temperature on relatively inexpensive buffered substrates, such as glass. Such films could have widespread application in photovoltaic and display technologies.

Description

REFERENCES CITED[0001]U.S. Patent Documents[0002]U.S. Pat. No. 4,717,688 January 1987 Jaentsch . . . 148 / 171[0003]U.S. Pat. No. 5,326,719 July 1994 Green et al. . . . 427 / 74[0004]U.S. Pat. No. 5,544,616 August 1996 Ciszek et al. . . . 117 / 60[0005]U.S. Pat. No. 6,429,035 B2 August 2002 Nakagawa et al. . . . 438 / 57[0006]U.S. Pat. No. 6,784,139 B1 August 2004 Sankar et al. . . . 505 / 230[0007]Other Publications[0008]Kass et al, Liquid Phase Epitaxy of Silicon: Potentialialities and Prospects”, Physica B, Vol 129, 161 (1985)[0009]Massalski et al, “Binary Alloy Phase Diagrams”, 2nd edition, (1990), ASM International[0010]Findikoglu et al, “Well-ordered thin Silicon Films with High Carrier Mobility on Polycrystalline Substrates”, Adv. Materials, Vol 17, 1527, (2005)[0011]Teplin et al, “A Proposed Route to Thin Film Crystal silicon Using Biaxially Textured Foreign Templates” Conference paper NREUCP-520-3897, November 2005[0012]Goyal et al., “The RABiTS approach: Using Rolling-assisted Biaxi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B32B5/16
CPCC03C17/3618Y10T428/24421C03C17/3649C03C17/3668C03C17/3678C03C2218/15C23C14/025C23C14/18C23C14/5873H01L31/0236H01L31/028H01L31/035281H01L31/0392H01L31/068Y02E10/50Y10T428/24372C03C17/3636H01L31/035227H01L31/03921H01L31/1804Y02E10/547Y02P70/50C30B25/02C30B11/12H01L21/02653
Inventor CHAUDHARI, PRAVEEN
Owner SOLAR TECTIC