Cordero Gallium Project
north central Nevada, USA
Uses (Sources: COMPOUND SEMIOnline, Strategies Unlimited, Resource-World.Net, and the USGS)
History: For over 30 years, world governments and industry have been working on Gallium Arsenide (Ga-As) based compound semiconductor devices. The exciting "new" field of gallium-nitride compounds is actually over 20 years old. Much of the early work was funded by U.S. and Soviet Cold War Treasuries to develop military satellite systems, night vision devices, photocells, and missile guidance components. In recent years, gallium has been processed into gallium-arsenide for the manufacture of semiconductor wafers used in cell phones, DVD players, chips and cells. Roughly 95% of US gallium is consumed in the manufacture of electronic components such as cell phones, DVD players, photovoltaic cells, integrated circuits, photo-detectors and LED's (Light Emitting Diodes). Prior to the development of gallium-arsenide based LED's in the late 1960's, gallium was little more than a laboratory curiosity. Since then, the uses and consumption of gallium have continued to grow.
Integrated Circuits: Over the last 15 years the use of gallium-arsenide (Ga-As) for high-speed semiconductors in the electronics field has matured to the point of replacing silicon-based chips in many integrated circuit applications. The integrated circuit has traditionally been the largest net consumer of Gallium, claiming slightly over 50% of the market as recently as 1999. The wireless field (cell phones) dominates new gallium use and global demand is expected to increase into the next decade. Electron transfer in Ga-As chips is much faster and cleaner than in many conventional silicon-based chips and far more stable at higher power demands. Speed and reliability are critical to communications devices such as cell phones, digital phone amplifier handsets, and increasingly as a simple, low-cost circuit option in other devices. The wireless products field includes: low noise amplifiers, power amplifiers, driver amplifiers, downconverters, digital switchs, frequency converters, and microwave/millimeter wave products.
The Ga-As Monolithic Microwave Integrated Circuit (MMIC) was originally developed for military and commercial satellites, and dishes, because it can deliver a wide wavelength range, making it crucial for satellite television. The Ga-As chip is also superior in withstanding extreme temperatures and radiation effects - traits ideal for use in aircraft, military applications, and spacecraft. For example, Ga-As semiconductors were key guidance components in the Patriot missiles used in the Gulf War.
Optoelectronics: The second largest user of gallium is in the rapidly emerging field of optoelectronics where gallium-based compound semiconductors are far superior to traditional silicon-based devices when it comes to light gathering or emitting capabilities. The "opto" in optoelectronics means light-related and refers to the ability of the compound to move light as photons. When combined with electronics the term optoelectronic is used. This field includes applications such as energy generation (photocells), light and heat detection, and the high profile communication/information processing industry. The all-optical network of fiberoptics, laser diodes, night vision devices, and LED's are current users of existing gallium compounds.
Medical: Gallium has recently been used very successfully in the medical field to combat aluminum (Al) - based bone loss in horses (Navicular disease) and is also showing promise in treating Al-based neurological disorders such as Alzheimer and Parkinson's diseases. Researchers are now recommending gallium nitride consumption for prevention and treatment of these Al-related conditions in humans. Gallium is also used in the detection of certain cancers.
Other Uses: Other significant uses for elemental Ga, include: high temperature thermometers and pressure gauges, high temperature mirror coatings, vacuum seals, and high temperature lubricants. As an alloy it is widely used with Ni and Co in dental fillings, Al-Ga cathodes in ultra-violet lamps, to make Mg corrosion resistant and stronger, with In to prolong the life of ball bearings, with In and Sn as a lubricant, and as a fusible alloy with In and Sn. Other little known, but emerging areas of use are in skis and snowboards, and emerging quantum well and quantum dot technology for wireless communications and laser applications.
Gallium Nitride - the Future: Present and future technological developments that will change the way we live promise greatly increased demand for Gallium in compound Ga-N semiconductors. The following quotation from the US Navy Office of Naval Research Program Officer John Zolper explains why Gallium "may turn out to be one of the most important materials of the new millennium":
A light bulb that lasts up to 10 years; a blue laser that will quadruple the storage capacity of a compact disc; microwave amplifiers for wireless communications systems that translate into better reception on your cell phone and fewer low-earth satellites and transmitting stations cluttering up the environment; transistors for a powerful new radar technology that may ride aboard the Navy's first all-electric ship; and aerospace components that can operate over a wide temperature range and remain unaffected by radiation.
Gallium nitride (Ga-N) competes with Indium-phosphide (In-P) in compound semiconductors as the latest and most exciting advance in fiberoptic communication networks due to reliability and the ability to move light at extremely high speeds. An even more exciting niche for this compound may be in high-brightness LED's (light emitting diodes) and laser diodes in the blues-end of the spectrum. As Ga-N bulk crystal development is perfected and made available on the market, it will be developed for next generation electronic devices that perform beyond the capability of the more mature silicon, Ga-As, and In-P technologies.
Laser Diodes: Recent advances in high-density data storage require Ga compounds in the laser diodes that operate at the short wavelength, blue-end of the spectrum, permitting far more data to be stored on CD's, DVD's, and Hard Drives. The data storage rates achieved with the blue spectrum laser diodes are 3-4 times that of conventional devices and are close to becoming commercially available.
High Brightness LED's: Conventional LED's have been in use for many years, but the newer High Brightness (HB-LED's) emit far more light from much less power by use of various Ga compound semiconductors. Full color outdoor LED signs have come onto the market in the mid-1990's and because they are bright, colorful, and able to except video feed, are becoming very popular. Colored LED's are also rapidly gaining use in automobiles as stop lamps and instrument panels. Because LED's in traffic lights use 80% less power and last much longer than the traditional incandescent light, they are increasingly used as replacements. Due to the recent energy crisis in California, Caltrans has retrofitted more than 200,000 signal lights with LED's.
Bright White Light Emitting Diode: The light emitting diode market appears to be on the brink of introducing mass-produced bright white light from very energy efficient diodes that last up to 10 years. As the industry moves towards blue LED's, epitaxial growth techniques become more stringent on the manufacturing end. The challenge is to move from growing the Ga-N compound on another substrate to manufacturing Ga-N wafers - an area garnering much attention at present. Once manufacturing issues such as the coating and packaging of the lamps, and color combinations have been optimized, mass production will be possible. The reward will be bright white light emitting diodes that are energy efficient, cool to the touch, cheap to produce, and very long lasting. Although early prototypes of the white LED's are on the market in nightlights and flashlights, perfected lighting and manufacturing techniques are still on the horizon. A number of companies, including GE and Philips, are working hard to perfect HB- White LED's and get them to market. What is currently a $1.2 billion market is expected to be a $3.4 billion market by 2005 according to Strategies Unlimited.
Integrated Circuits: Advances in the use of Ga-N for integrated circuits for commercial and military use is projected to grow rapidly over the next decade. Another important application may be in microwave amplifiers for wireless communications systems providing better cell phone reception with less need for low-earth satellites and transmitting stations. The military expects further breakthroughs in transistors for powerful new radar and aerospace components able to withstand wide temperature and severe radiation.
Environmental Uses: Energy savings provided by LED's, colored HB-LED's, and Bright White LED's can be up to 80% over conventional incandescent lights. The perfection of the Bright White LED's will represent a revolution in lighting as less energy is used, virtually no heat generated, and less wasted materials generated due to the longevity of the diode.
More efficient gallium-based photovoltaics have recently been tested by European interests basing their work on that of NOAA's NREL laboratories in the United States. Recent advances in this area could mean substantial improvements in solar power generation.
In 1999, a modified quantum cascade laser diode at Bell Labs, demonstrated the ability to simultaneously emit light at multiple, widely separated wavelengths. The key to this success was an Al-In-As / In-Ga-As semiconductor compound. Potential applications for this new laser diode include: pollution monitoring, non-invasive early detection of disease, and catalytic converter monitoring.