GaAs is a III–V compound semiconductor composed of the element gallium (Ga) from column III and the element arsenic (As) from column V of the periodic table of the elements.

Why is GaAs a semiconductor?

GaAs have a direct bandgap unlike many other semiconductors implying it can emit light with high efficiency. Being a direct bandgap material, it is resistant to radiation damage enabling its use in optical windows and space electronics in high power applications.

Is GaAs an alloy?

Aluminium gallium arsenide (also gallium aluminium arsenide) (AlxGa1−xAs) is a semiconductor material with very nearly the same lattice constant as GaAs, but a larger bandgap. The x in the formula above is a number between 0 and 1 – this indicates an arbitrary alloy between GaAs and AlAs.