Gallium Arsenide
Title: Gallium Arsenide
CAS Registry Number: 1303-00-0
Molecular Formula: AsGa
Molecular Weight: 144.64
Percent Composition: As 51.80%, Ga 48.20%
Line Formula: GaAs
Literature References: Prepd by passing a mixture of hydrogen and arsenic vapor over gallium(III) oxide at 600°: Goldschmidt, Skr. Akad. Oslo 1926, no. 8, pp 34, 100; Ber. 60, 1289 (1927). Simplified procedure: Juza, Schulz, Z. Anorg. Allg. Chem. 275, 65 (1954); Minden, Sylvania Technol. 11, no. 1, p 19 (Jan. 1958). Vapor phase crystal growth: McAleer et al., J. Electrochem. Soc. 108, 1168 (1961). Use in high-speed microcircuits: A. L. Robinson, Science 219, 275 (1983). Review of toxicology and human exposure: Toxicological Profile for Arsenic (PB2000-108021, 2000) 468 pp.
Properties: Cubic crystals. mp 1238°. Dark gray with metallic sheen. Hardness 4.5. d425 5.31. Thermal expansion coefficient: 5.9´10-6. Thermal conductivity 0.52 watt units. Specific heat 0.086 cal/g/°C. Molten gallium arsenide attacks quartz, therefore graphite boats or quartz boats, which are carbon coated by pyrolytic decompn of methane, should be used in zone refining. GaAs single crystals have been grown by the Czochralski technique and by the floating zone method. Extensive twinning occurs. Intrinsic electron concn 107. Energy gap at room temp 1.38 electron volts. Electron mobility 8800 cm2/volt sec. Hole mobility 450 cm2/volt sec. Effective mass for electrons 0.06 m0. Lattice constant 5.654Å. Dielectric constant 11.1. Intrinsic resistivity at 300 K = 3.7´108 ohm-cm. Electron lattice mobility at 300 K = 10,000 cm2/volt-sec. Intrinsic charge density at 300 K = 1.4´106/cm3. Electron diffusion constant at 300 K = 310 cm2/sec. Hole diffusion constant = 11.5 cm2/sec.
Melting point: mp 1238°
Density: d425 5.31
Use: In semiconductor applications (transistors, solar cells, lasers).

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