Compound semiconductor

A compound semiconductor is a semiconductor where the main structure of the material is made from more than one chemical element.

 History 
The earliest semiconductors were made of galena, a mineral mostly made of lead(II) sulfide. Unlike most compound semiconductors, galena can be found in nature. When single-element semiconductors made of germanium or silicon were discovered, they replaced galena for most applications, but compound semiconductors were still used in research.

 Common types 
Types of semiconductor are normally named by the old names of groups in the periodic table. These use Roman numerals to label columns or groups of columns from I to VIII, repeating twice across the periodic table: Group I contains what is now group 1 elements and group 11 elements, Group II contains group 2 elements and group 12 elements, and so on. The one exception to the pattern is Group VIII, which includes all of the group 8 elements, group 9 elements, group 10 elements, and noble gases (group 18 elements) - but this exception does not matter much to semiconductors.

 IV 
While many carbon group semiconductors use pure elements rather than compounds, mixtures of these elements are sometimes considered compound semiconductors. Silicon carbide is the most common mixed group IV semiconductor. It has similar properties to silicon but works at higher temperature and voltage.

 III–V 
III–V semiconductors are made from boron group elements and pnictogens. They are usually made with gallium or indium from Group III and phosphorus or arsenic from Group V. Gallium arsenide is the second most common semiconductor after silicon.

Some other important III-V semiconductors are gallium nitride, gallium phosphide, indium phosphide, indium gallium phosphide, and indium gallium arsenide.

 II-VI 
II-VI semiconductors are used in solar cells. Cadmium telluride is used in some of the world's largest solar farms. It is one of the only compound semiconductors to do as well as silicon for solar power.

 I-VII 
Semiconductivity has been found in some halides of copper and silver. Their properties make them interesting to researchers trying to make better solar cells, but their use is limited because it is hard to grow crystals of the right size and quality.

 Sources