Читать книгу Semiconductor Basics - George Domingo - Страница 33

Semiconductors have different energy gaps measured in electron‐volts (eV), the energy of an electron under an applied voltage of 1 V (Figure 2.11). As you may expect, an electron‐volt is a very small amount of energy (e = 1.602 × 10⁻¹⁹ coulombs). The energy gaps of the most commonly used semiconductors – germanium, silicon, and gallium arsenide – are 0.67, 1.12, and 1.43 eV, respectively. Silicon is the most commonly used because it is easier to grow as pure crystals with no (or an insignificant number of) impurities and imperfections, and it is also easier to inject a controlled number of impurities. In the next chapter, I discuss why purity and the ability to add a controlled number of impurities are so important.

Figure 2.11 There is a large difference in energy gaps in semiconductors, from a very low value for InSb (0.17 eV) to GaAs (1.43 eV). Notice that the energy gap changes slightly as the temperature changes: about 5% for silicon between absolute zero and room temperature.

There is an interesting website with a huge amount of information on the elements: http://periodictable.com/Elements/050/data.html. Clicking any element in the periodic table will tell you its properties. Furthermore, if you click any property, it will tell you the value of that property for all the elements in the periodic table. It is interesting to see, using this website, that the great majority of elements are conductors. According to this site, of all the elements in the periodic table, 76 are conductors, 5 are insulators, and only 3 are semiconductors: Si, Ge, and Te. Te has an energy gap of 0.45 eV. The rest of the elements are either gases or have unknown values.