ABSTRACT
In the sciences, especially chemistry, physics, materials science, and electronics, atomic theory is a scientific theory that provides basic knowledge about matter, which is composed of tiny units called atoms. In atomic theory, the Rutherford–Bohr model, also called the Bohr atomic model, was discovered in 1913. Materials that have conductivity lying between conductors and insulators are called semiconductors. The electrical properties of semiconductors can be studied on the basis of the resistivity of the materials. Light emission from semiconductor materials occurs due to the movement of an electron from the lower to the most excited states. Semiconductors act as insulators at room temperature, and the electrons are trapped within the atoms. The conductivity of the semiconductor increases with increase in temperature. The conductivity of semiconductor materials depends on carrier concentration and mobility. An extrinsic or doped semiconductor is a key component of many electronic devices. A unipolar semiconductor device is formed by the combination of p-type and n-type semiconductors.
