By Mocvd Technology Of Gan Materials Epitaxial Process

LED is a kind of electroluminescent devices that has developed rapidly since its invention in 1960s, especially after 1990s. With the sustaining development and implementation of new structures, new materials and new processes, its performance has been greatly improved. In the background of times of advocating energy-saving & emission-reduction, LED is applied widely in more and more sectors such as lighting, display and city-sight decoration due to its characteristics of lower energy consumption, higher efficiency and longer lifetime.As the epitaxial process is a very important step during the whole process of LED fabrication, this dissertation expatiated and discussed the epitaxial equipment, Metal-Organic Chemical Vapor Deposition (MOCVD), its operation principle and process, and the fundamentals of LED.MOCVD is a key equipment in the LED production line. The performance of end products is greatly dependent on the MOCVD process. This dissertation introduced the main structure, working principle/process and relevant parts of the MOCVD equipment, including gas transportation, reactor process and structure, temperature and pressure control systems, exhaust treatment and safety equipment.After presenting the fundamentals of LED the dissertation discussed the main factor affecting the efficiency, the carrier recombination rate. The Multi-Quantum-Well (MQW) structure was then introduced to improve LED's performance. The quantum effect in this structure can limit the electrons and holes in certain region so that the carrier recombination rate can be enhanced significantly.Base on above consideration the dissertation introduced a proper epitaxial process and present some obtained results. As the epitaxy of the GaN-Base wafers is the core technology of the white LED and the original driver of the semiconductor lighting technology, this dissertation focused on GaN material. Due to the serious lattice mismatch between GaN and the sapphire substrate, our process adopted two-step epitaxy to obtain better GaN epi-layer by first growing a thin layer GaN as buffer layer at 500～600℃and then further growing high-quality crystal layer at higher temperature as 1050℃.