Manufacturing Technology for High-Performance Optoelectronic Devices

To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed.

Please login or register to make a comment!

ASTROPOWER, INC. LEDs That are Four Times as Bright Although LEDs are used in many applications where digi- tal readout is needed, they have limitations. They do not emit much light, so they cannot be seen at a distance.

If they produced really bright light, LEDs would be even more widely used than they are already. This ATP project with AstroPower, a small Delaware company incorporated in 1989, developed a new approach to production-scale liquid-phase epitaxy (LPE). The company has fabricated LEDs in a way that significantly increases, by a factor of four, the brightness of the light they emit.

A New Approach LPE is a widely used technique that involves melting a semiconductor material and letting it crystallize on a sub- strate. AstroPower 9s novel enhancement, the first technical goal of the project, involved the use of a thermal gradient that promotes the growth of the epitaxial layer laterally much faster than vertically from the substrate. Company researchers made significant advances in understanding growth processes for compound semiconductor materials and in applying LPE to lateral growth over buried reflec- tors and other components.

The technology can be used for volume production of low-cost compound semiconduc- tor devices 4 those made from a ... more. less.

compound of elements, such as gallium arsenide, rather than a single element. AstroPower 9s second technical goal was to develop the technology to automate the new LPE growth process in integrated factory-scale fabrication equipment. Company researchers succeeded in designing and assembling a modular prototype production growth system that has ELECTRONICS/COMPUTER HARDWARE/COMMUNICATIONS 101 ASTROPOWER, INC. Manufacturing Technology for High-Performance Optoelectronic Devices O ptoelectronic devices 4 from light-emitting diodes (LEDs) and solar cells to lasers and detectors 4 are abundant in everyday life. Millions of LEDs are used in automobile dashboards and consumer electronic products (clocks, radios, VCRs, CD players, coffee brewers, and microwave ovens), as well as in commercial and industrial products such as fax machines, copiers, and printers. COMPOSITE PERFORMANCE SCORE (Based on a four star rating.) 55 A large area solar grade silicon sheet emerging from a silicon growth reactor which incorporates new ATP-funded technology. . . . made significant advances in understanding growth processes for compound semiconductor materials . . . already significantly shortened production scale-up times for currently fabricated products, as well as for potential products under consideration by customers. Market Developments Upset Initial Commercialization Plans Commercialization of the enhanced compound semicon- ductor devices in high volumes has not yet happened. An initial goal, to produce high volumes of red LEDs, has been stymied by market developments. The Japanese have come to dominate the market for red LEDs, which have become a commodity product. Although AstroPower has a technical advantage in producing the devices, the value of this market to the company is quite small, since the cost of entering the market is too high to make such a venture profitable. Use of the Technology for Current Product Lines Knowledge developed in the ATP-funded project, espe- cially advances in understanding epitaxy technology, has proven useful across all company production activities, AstroPower officials say. They report that the company 9s product lines have all grown rapidly in recent years, and they attribute much of the growth to the ATP project. All of AstroPower 9s compound semiconductor-based products incorporate epitaxial growth in their fabrication. This includes their flagship product, the Silicon-Film" solar cell. Silicon-Film" is a continuous production process to manufacture crystalline silicon sheets and layers. 102 ASTROPOWER, INC. PROJECT: To develop new crystal growth methods and high-throughput manufacturing technology for fabricating light detectors and emitters with integrated reflecting mirrors. Duration: 7/15/1992 to 7/14/1995 ATP Number: 91-01-0142 FUNDING (in thousands): ATP$1,423 47% Company 1,580 53% Total$3,003 ACCOMPLISHMENTS: The company achieved the goals of the ATP project: developing new epitaxial growth methods, as well as new processes for plant-scale industrial production operations. Evidence of the company 9s achievements are that it: s received four patents related to the ATP project technology; cColumnar- Grained Polycrystalline Solar Cell and Process of Manufacture d (No. 5,336,335: filed 10/9/1992, granted 8/9/1994) cHetero-Epitaxial Growth of Non-Lattice Matched Semiconductors d (No. 5,356,509: filed 10/16/1992, granted 10/18/1994) cColumnar-Grained Polycrystalline Solar Cell and Process of Manufacture d (No. 5,496,416: filed 8/5/1994, granted 3/5/1996) cSemiconductor Device Structures Incorporating cBuried d Mirrors and/or cBuried d Metal Electrodes d(No. 5,828,088: filed 9/5/1996, granted 10/27/1998); s demonstrated the application of the new epitaxial production technology to optoelectronic device structures that have integrated reflecting mirrors for enhancing light output (an ultrabright light-emitting diode (LED) with buried reflectors), achieving a fourfold increase in brightness; s completed scale-up of liquid-phase epitaxy (LPE)-growth technology to a high-throughput, production-scale process; s significantly shortened production scale-up times for specific products, compared with previous manufacturing processes; s constructed a demonstration production facility to implement the technology; and s conducted an initial public offering of stock in February 1998, raising $16.7 million. CITATIONS BY OTHERS OF PROJECT 9S PATENTS: See Figure 4.3. COMMERCIALIZATION STATUS: Direct commercialization of ultrabright red LEDs, a proposed initial goal of the project, did not occur, mainly due to economic and market developments. Knowledge of new crystal growth methods acquired during this project con- tributed, however, to the enhancement of fabrication methods for the company 9s Silicon-Film" solar cell and for other compound semiconductor devices. OUTLOOK: AstroPower has applied the ATP-funded crystal growth technology to its current manufacturing processes, improving productivity and lowering costs. It also plans to use the technology for several breakthrough devices when appropriate market size has been achieved; if such markets develop substantially, the outlook is promising. Two significant products that are nearing introduction are combustion sensors based on gallium-phosphorus compounds, and avalanche photodiodes and detectors based on indium-gallium-arsenic-antimony compounds. Composite Performance Score: 55 COMPANY: AstroPower, Inc. Solar Park, 461 Wyoming Road Newark, DE 19716-2000 Contact: James B. McNeely Phone: (302) 366-0400 Number of Employees: 86 at project start; 160 at the end of 1997 PROJECT HIGHLIGHTS . . . succeeded in designing and assembling a modular prototype production growth system . . . Shortened Production Scale-Up Times The success of the ATP-funded project ensures that new and innovative optoelectronic devices will have signifi- cantly shorter production scale-up times than were possi- ble before the project. The establishment of a technology that permits low-cost, high-throughput synthesis of com- pound semiconductor structures is potentially useful for many optoelectronic device products. It can be used, for example, in making specialty devices on a job-order basis using gallium arsenide, gallium arsenide-on-silicon, indi- um phosphorus, and a host of other unexplored alloys. These devices are used in the fabrication of common products like detectors, solar cells, sensors and light-emit- ting products. The new technology can also be used in the production of highly sophisticated devices such as vertical cavity surface emitting lasers and resonant optical cavity detectors with back reflectors. AstroPower intends to incorporate this technology in a number of breakthrough devices that it can produce in sufficiently large quantities when appropriate market size has been achieved. Two significant applications are near- ing product introduction. The first is combustion sensors, based on gallium phosphorus compounds, that can be used for flame control in internal combustion engines and utili- ty burners. The second is avalanche photodiodes and detectors, based on indium-gallium-arsenic-antimony and indium-arsenic-antimony-phosphide compounds, that can be used for light direction and range instruments, collision avoidance, atmospheric gas measurements, weather pre- diction, spectroscopy, blood gas analysis, and noninvasive medical analysis. These two products are currently in pilot production and are being tested by NASA, the Air Force, and industrial companies. Company Growth At the beginning of the ATP project in 1992, AstroPower had annual product sales of $1 million. By 1997, sales had grown to $16 million. And in February 1998, AstroPower successfully conducted an initial public offering of stock, raising $16.7 million. AstroPower is convinced that had it not conducted the ATP-funded project, its growth experience (as measured by product sales) would have been set back by three years, the length of the ATP project. This belief is based on the use of improved epitaxial growth technology across all of its product lines, its application of manufacturing automa- tion processes to all of its manufacturing operations, and to the overgrowth of semiconductor materials on dissimilar substrates as well as on mirrors, insulators, and conducting planes. Without the ATP funds, AstroPower says it would not have carried out the project. Potential Large Economywide Benefits AstroPower noted at the beginning of its ATP project in 1992 that it expected in a project like this that products might take as long as 10 years to move from initial tech- nology development to new product sales. The demon- stration production facility AstroPower developed is capa- ble of producing millions of LEDs or other LPE-based optoelectronic devices per month. When sufficient demand for the new products emerges, AstroPower plans to construct an optoelectronic semiconductor chip-manu- facturing facility for new products made possible by the innovative LPE-growth technology. 103 ASTROPOWER, INC. An initial goal, to produce high volumes of red LEDs, has been stymied by market developments . . . red LEDs have become a commodity product. . . . had it not conducted the ATP-funded project, its growth experience . . . would have been set back by three years. Benefits are already accruing to purchasers of the company 9s solar cells, which have higher quality and cost less than they did before the ATP project. . . . the company 9s product lines have all grown rapidly in recent years, with much of the growth attributed to knowledge developed in the ATP-funded project. 104 ASTROPOWER, INC. Original Patent Second Generation Patent Third Generation Patent Fourth Generation Patent Fifth Generation Patent PATENT TREE KEY 1995 1996 1997 1998 1999 1994 5496416 Astropower 5486237 Sanyo Elec. 5336335 Astropower 5356509 Astropower 5828088 Astropower 5821562 Sharp 5837569 Sharp 5766989 Matsushita Electric Industry 5797999 Sharp 5744864 U.S. Philips Corp. 5897366 Motorola 5956581 Semiconductor Energy Laboratory 5885889 NEC 5888295 Micron Tech. 5913544 Sharp 5976481 Tokuyama Corp. RE36156 Astropower 5965005 National Science Council 5930608 Semiconductor Energy Laboratory 5946560 Semiconductor Energy Laboratory 5994164 PennState 5970369 Fujitsu Ltd. 6028326 Semiconductor Energy Lab 5619044 Sharp 5670793 Hitachi Ltd. 2000 5825068 Integrated Device Tech. 5811021 Hughes 5496416 Astropower 5605860 Matsushita Figure 4.3 Patent Tree for Project Led by AstroPower, Inc.: Citations by Others of AstroPower, Inc. Patents 105 ASTROPOWER, INC. Benefits are already accruing to purchasers of the company 9s solar cells, which have higher quality and cost less than they did before the ATP project. If the company succeeds in bringing to market additional products that use the new technology, even more benefits will accrue to its customers. Because of substantial uncertainty about these events, it is too speculative at this time to try to predict the magnitude of these future benefits. Cross-sectional photomicrograph of a light emitting diode showing device active layers and buried mirror overgrowth.

less