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Gallium arsenide

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Use of gallium arsenide in medical applications
Carr, K.L.   
Microwave Med. Syst. Inc., Acton, MA;
This paper appears in: Gallium Arsenide Integrated Circuit (GaAs IC) Symposium, 1995. Technical Digest 1995., 17th Annual IEEE
Meeting Date: 10/29/1995 -11/01/1995
Publication Date: 29 Oct-1 Nov 1995
Location: San Diego, CA ,   USA
On page(s): 10-13
References Cited: 12

Microwave technology can be used to solve many medical problems where conventional technology has proven inadequate. This is particularly true for applications involving the generation of heat and the measurement and monitoring of temperature. Through cost-effective fabrication techniques based upon MMIC technology, this microwave technology has now become affordable. Several applications illustrating the significance of MMIC technology will be discussed. MMS's IV Injection-Site Monitor, for example, is based on passive microwave radiometric monitoring of subcutaneous tissue temperature. This technique is based upon the assumption that an unwanted accumulation of liquid (i.e., an extravasation into the tissue surrounding the infusion site) will result in a temperature differential. An extravasation is defined as the unwanted occurrence of infiltration of fluid during IV infusion beyond the vein or artery into the surrounding tissue. Extravasations of IV fluids in children can have serious consequences when gross extravasations occur. Skin necrosis can occur, which may require treatment with skin grafting. These advanced sequelae are less frequent in the adult population, but in newborns and young children they are much more prevalent and can be catastrophic. Neonates and infants are unable to communicate pain and are more prone to tissue necrosis. To address this application, the sensitive radiometer must be small and lightweight to meet the requirements of the pediatric (including neonatal) patient population

Gallium arsenide (GaAs) and gallium nitride (GaN)
components represented about 98% of domestic gallium consumption. About 42% of the gallium consumed was
used in optoelectronic devices, which include light-emitting diodes (LEDs), laser diodes, photodetectors, and solar
cells. Integrated circuits represented 49% of gallium demand. The remaining 9% was used in research and
development, specialty alloys, and other applications. Optoelectronic devices were used in areas such as aerospace,
consumer goods, industrial components, medical equipment, and telecommunications. Integrated circuits were used
in defense applications, high-performance computers, and telecommunications.

The researchers used GaAs in an effort to miniaturize the detectors, making them more portable for such applications as detecting smuggled fissile material, which could be used to fuel nuclear weapons, at ports and airports, and for use by international nuclear nonproliferation inspectors. Currently, two types of neutron detectors are in use—those based on a tube filled with gas that is ionized by neutrons and those based on silicon. The GaAs-based detectors are made by coating semi-insulating GaAs with isotopically enriched boron or lithium and can be manufactured using conventional processes. Using GaAs rather than silicon has several advantages. The detectors can be made smaller, require less than 50 volts of operating power, and operate at room temperature. Replacing silicon with GaAs also improves the lifetime of the detector when it is used in areas with high radiation levels (Newey, 2002b).

Indium phosphide components can be substituted for GaAs-base infrared laser diodes in some specific-wavelength applications, and GaAs competes with helium-neon lasers in visible laser diode applications. Silicon is the principal competitor for GaAs in solar cell applications. GaAs-base integrated circuits are used in many defense-related applications because of their unique properties, and there are no effective substitutes for GaAs in these applications. GaAs in heterojunction bipolar transistors is being challenged in some applications by silicon-germanium.