Optical Band Gap of Thin Film Semiconductors

Semiconductors are materials whose electrical conductivity lies between conductors and insulators. They play a very important role in modern electronics and are used in devices such as diodes, transistors, solar cells, and integrated circuits. The study of semiconductors has become essential because almost all electronic devices depend on them for proper functioning. In recent years, thin film semiconductors have gained significant attention due to their unique properties and wide range of applications. Thin films are extremely thin layers of material, typically in the nanometer or micrometer range, deposited on a substrate such as glass or silicon. These films exhibit different electrical and optical properties compared to bulk materials, making them highly useful in advanced technologies. One of the most important properties of semiconductors is the optical band gap. The band gap is defined as the energy difference between the valence band and the conduction band. It determines how a material interacts with light and plays a crucial role in optoelectronic devices like LEDs, photodetectors, and solar panels. By studying the optical band gap, we can understand how efficiently a material can absorb or emit light. The optical band gap of thin film semiconductors can be determined using various experimental techniques, among which UV-Visible spectroscopy is the most common. The data obtained from such experiments is analyzed using methods like the Tauc plot, which helps in calculating the band gap accurately. This study is essential for designing materials with desired optical properties. In this project, we focus on the optical band gap study of thin film semiconductors. We explore their theoretical background, experimental methods, and analysis techniques. The aim is to understand how different factors such as thickness, temperature, and preparation methods influence the band gap and overall performance of the material.The absorption coefficient of semiconductor thin films is closely related to the photon energy and provides useful information regarding electronic transitions. By analyzing the absorption spectra obtained through UV-Visible spectroscopy, the optical band gap can be estimated accurately. The Tauc relation is commonly used for this purpose, where the graph between (αℎ𝜈)nand ℎ𝜈is plotted to determine the band gap energy. The extrapolation of the linear portion of the graph gives the optical band gap value of the material. (αℎ𝜈)n = 𝐴(ℎ𝜈 − 𝐸g)