The commonly used semiconductor materials are silicon (SI) and germanium (GE). Compound semiconductors are prepared by alloying different elements. One example is gallium arsenide (GaAs). There are two types of semiconductors, intrinsic semiconductors and extrinsic semiconductors，When acceptor or donor substances (called dopants) are added to the semiconductor, electrons are injected through the donor impurity dissociation guide band or the acceptor impurity captures valence band electrons to produce free carriers, which makes the intrinsic semiconductor produce additional conductivity and become an extrinsic semiconductor.
Intrinsic semiconductors and extrinsic semiconductors are two types of semiconductor materials. The difference between intrinsic and extrinsic semiconductors is that intrinsic semiconductors are pure forms of semiconductor materials. External semiconductors are impure semiconductors formed by adding impurities to pure semiconductors.
No, in the case of an intrinsic semiconductor, any external impurities will be doped, and an external semiconductor is formed by adding trivalent or pentavalent impurities to the semiconductor material.
For intrinsic semiconductors, the Fermi level is just in the middle of the forbidden band. The band gap of silicon (GA) is 1.6V, germanium (GE) is 0.66v and gallium arsenide (GaAs) is 1.424v. External semiconductor，Gallium arsenide (GaAs) is an intrinsic semiconductor. One of its important properties is that it can convert electrical energy into light. The unit chemical formula of GaAs has 8 valence electrons (3 from Ga atoms and 5 from as atoms), which means that its valence band has been filled. However, if sufficient electrical energy is provided, valence band electrons can be excited to the conduction band. The excited electron emits photons when it returns to the valence band, and its wavelength is proportional to the energy related to the band gap