Development and optimization of various inorganic and organic semiconductors based heterostructures for optoelectronic applications

Abstract

Optoelectronics deal with the optical interaction on the electronic responses in some semiconducting materials which are optically active. Common examples are photovoltaic cells (which absorb light and converts it into electricity), photodiodes or laser diodes (generating light by electron-hole recombination) etc. While being irradiated with a light of energy greater than or equal to its bandgap value, electrons jump from valence band to conduction band of the semiconductor and constitute a photocurrent. Photodetectors are used for detection of light based on this principle and are fabricated depending on requirements. The need for a visible-blind detector arises from the fact that the detectors should be sensitive only to short wavelength ultraviolet (UV) light and not to visible light. The fabrication of photodetectors of various sizes includes complex lithography/electronics depending on whether we need a high voltage application or detection of extremely small voltages. Finally there is always a trade-off between the size, robustness, cost as well as ease of fabrication. Si photodetectors have band gap (~1.1 eV) based limitations adding to high cost filters and high temperature sensitivity, thus shifting our focus to wide band gap semiconductors like Gallium Nitride (GaN), Zinc Oxide (ZnO) etc.. Both GaN and ZnO are extraordinary candidates for ultraviolet photodetectors due to their high carrier mobility, radiation hardness and thermal stability. GaN/ZnO heterostructures are interesting because of similar physical properties of these two direct band gap semiconductors allowing the growth of high quality ZnO layer on GaN layer, thereby encouraging lower imperfection in such heterostructures. newline