1.GalliumArsenide, GaAs - After silicon second the most common semiconductor, energy gap Eg = 1.43 eV, direct bandgap; crystal structure - zinc blend, lattice constant 5.65 Ang., index of refraction 3.3, density 5.32 g/cm3, dielectric constant 12.9, intrinsic carrier concentration 2.1 x 106 cm-3, mobility of electrons and holes at 300 K - 8500 and 400 cm2/V-s, thermal conductivity 0.46 W/cm-oC, thermal expansion coefficient 6.86 x 10-6 oC-1; thermally unstable above 600 oC due to As evaporation; does not form sufficient quality native oxide; mechanically fragile; due to direct bandgap commonly used to fabricate light emitting devices; due to higher electron and hole mobilities, also foundation of the variety of high-speed electronic devices; bandgap can be readily engineered by forming ternary compounds based on GaAs, e.g. AlGaAs.
2.Gallium Nitride, GaN - wide bandgap III-V semiconductor with direct bandgap 3.5 eV wide; among very few semiconductors capable of generating blue radiation, GaN is used for blue LEDs and lasers; intrinsically n-type semiconductor but can be doped p-type; GaN is formed as an epitaxial layer; Lattice mismatch remains a problem, creating a high defect density. Incorporation of Indium (InxGa1-xN) allows control of emission from green to violet (high and low In content respectively). GaN can also be used in UV detectors that do not respond to visible light. GaN has a Wurtzite(W) or Zinc Blend(ZB) crystal structure. Lattice constant [A] 3.189(W) 5.186(ZB); Density[g/cm3] 6.15(W) 6.15(ZB); Atomic concentration [cm-3] 8.9 x 1022(W) 8.9 x 1022(ZB); Melting point [oC] 2,500(W) 2,500(ZB); Thermal conduct.[W/cm oC] 1.3(W) 1.3(W); Thermal expansion coefficient[oC-1] ~1x10-6; Dielectric constant (static) 8.9(W) 9.7(ZB); Refractive index 2.4(W) 2.3(ZB);
3.GaP - Crystal structure zinc blend; Lattice constant [A] 5.45; Density [g/cm3] 4.14; Atomic concentration [cm-3] 4.94 x 1022; Melting point [oC] 1457; Thermal conductivity [W/cm oC] 1.1; Thermal expansion coefficient[1/oC] 4.65x10-6; Dielectric constant 11.1; Refractive index 3.02; Energy gap [eV] 2.26; Type of energy gap: direct; Electron mobility [cm2/V sec] 250; Hole mobility [cm2/V sec] 150;