Common examples are GaAs or InP. These compound semiconductors belong to the III-V semiconductors so called because first and second elements can be found in group III and group V of the periodic table respectively. In compound semiconductors, the difference in electro-negativity leads to a combination of covalent and ionic bounding. The subscript x refers to the alloy content of the material, what proportion of the material is added and what proportion is replace by the alloy material. Once again, the subscripts denote the proportion elements that constitute the mixture of elements. Alloying semiconductors in this way allows the bandstructure and lattice spacing of the crystal to be altered.
Intrinsic semiconductors are essentially pure semiconductor material.
The semiconductor material structure should contain no impurity atoms. Elemental and compound semiconductors can be intrinsic semiconductors. At room temperature, the thermal energy of the atoms may allow a small number of the electrons to participate in the conduction process. Unlike metals, the resistance of semiconductor material decreases with temperature. As the temperature increases, the thermal energy of the valence electrons increases, allowing more of them to breach the energy gap into the conduction band.