Mô đun này là giúp cho người học phát triển được kiến thức và kỹ năng cần thiết về sử dụng Tiếng Anh chuyên ngành để đọc, hiểu các tài liệu kỹ thuật trong lĩnh vực điện tử công nghiệp cũng như giao tiếp Tiếng Anh chuyên ngành trong môi trường làm việc tại doanh nghiệp. | Substances like carbon, silicon, germanium whose electrical conductivity lies in between the conductors and insulators are known as semiconductors. The valence band of these substances is almost filled, but the conduction band is almost empty. The forbidden energy gap between valence and conduction band is very small (1ev). Therefore comparatively a smaller electric field is required to push the valence electrons to the conduction band. This is the reason, why such materials under ordinary conditions do not conduct current and behaves as an insulator. Even at room temperature, when some heat energy is imparted to the valence electrons, a few of them cross over to the conduction band imparting minor conductivity to the semiconductors. As the temperature is increased, more valence electrons cross over to the conduction band and the conductivity of the material increases. Thus these materials have negative temperature co-efficient of resistance.
