Basic physical properties of gallium arsenide materials:
GaAs semiconductor material is a direct band gap structure with double energy valleys. The crystal is dark gray with metallic luster. GaAs is insoluble in hydrochloric acid at room temperature, can react with concentrated nitric acid and is easily soluble in aqua regia. GaAs is stable in water vapor and oxygen at room temperature. When heated to 6000c, oxidation begins, and when heated to more than 8000C, dissociation begins. The lower the effective mass, the faster the electron velocity. The effective mass of electrons in GaAs is 1 / 15 of that of free electrons, which is 1 / 3 of that of silicon. The switching speed of transistors made of GaAs is 3 ~ 4 times faster than that of silicon.
Gallium arsenide lattice is composed of two face centered cubic (FCC) sublattices (the lattice points are the two sublattices of arsenic and gallium respectively) displaced by 1 / 4 along the diagonal of the space body. This crystal structure is called sphalerite structure in physics.On average, there are four valence electrons per atom between them, which can be used to form tetrahedral covalent binding. These compounds are mainly covalently bound, but mixed with some ionic binding properties. This is because the electronegativity of group V elements is greater than that of group III elements. When forming a crystal, some electrons will be transferred from atoms with low electronegativity (Group III elements) to atoms with high electronegativity (Group V elements). This transfer (polarization) of charge makes group III elements positively charged and group V elements negatively charged. If the concept of effective charge Z * e is used to describe the degree of charge transfer, the "covalent bond" model can think that GaAs crystal is mainly covalent binding, but mixed with some ion binding properties, and each ion has effective charge Z * e.
Gallium arsenide is a III-V semiconductor material. Its zinc blende crystal structure and direct band gap structure make it have better properties than silicon and germanium. Gallium arsenide has higher electron mobility and saturation mobility, and has unique semi insulation. Moreover, gallium arsenide material also has the characteristics of heat resistance, radiation resistance and sensitivity to magnetic field, which makes gallium arsenide material have special uses and diversity. Its application has been extended to the fields that silicon and germanium devices can not achieve.