Gallium arsenide has higher electron mobility than silicon, so most carriers also move faster than those in silicon. GaAs also has the characteristics of reducing parasitic capacitance and signal loss. These characteristics make integrated circuits faster than circuits made of silicon. The increased signal speed of GaAs devices allows them to respond to high-frequency microwave signals in communication systems and accurately convert them into electrical signals. Silicon based semiconductors are too slow to respond to microwave frequencies. Gallium arsenide has higher material resistivity, which makes it easy to isolate semiconductor devices manufactured on gallium arsenide substrate without loss of electrical performance
Silicon and germanium belong to indirect band gap semiconductors. The bottom of the conduction band and the top of the valence band are not at the same point in K space. They form a half full energy band, which not only absorbs energy (radiated photons, HV = EC EV), but also changes momentum (radiated phonons, momentum) Δ P = reduced Planck constant * k), as an electronic device.
GaAs is a direct band gap semiconductor. The minimum conduction band energy and the maximum valence band energy are at k = 0. To form a half full energy band, you only need to absorb energy (radiate photons) as an optical device. Supplement: if impurities are doped into the semiconductor and the composite central energy level is introduced, three spectral lines HV1 = EC et, HV2 = et EV, HV3 = EC EV will appear when radiating photons, and the spectral lines will be red shifted.
GaAs devices are developing rapidly. Although the idea of replacing silicon and germanium with gallium arsenide has not been realized, it has shown excellent performance in laser, luminescence and microwave. Gallium arsenide has been used to manufacture high-speed integrated circuits, which puts forward higher requirements for material quality, which promotes the further research of gallium arsenide materials.