Studying On Free-Standing GaN Growth By HVPE

With the development of semiconductor materials, the third generation of semiconductors, which are represented by gallium nitride (GaN) and other Ill-nitride wide gap materials, have attracted more and more attention, because of their superior advantages. GaN and its ternary alloys have widespread applications in the fabrication of high bright blue, green, and white light emitting diodes (LEDs), short wavelength laser, ultraviolet (UV) detector and high temperature electronic devices etc. However, the high density dislocations in GaN have fatal effects on devices' performance. And the high density dislocations results from heteroepitaxy. To achieve homoepitaxy growth of GaN and then obtain high quality and large size GaN films, researchers are trying various methods to realize the growth of free-standing GaN.This paper, with the goal of fabricating free-standing GaN, discussed the system design of Hydride Vapor Phase Epitaxy (HVPE), GaN growth mechanisms and growth modes, optimization of growing thick GaN film with high quality, GaN characterization, and the realization of free standing GaN film, respectively.By calculations it was confirmed that lattice mismatch and thermal coefficient mismatch are major causes for dislocations generating in hetero expitaxy growth of GaN. By etching, all kinds of dislocations in GaN were observed under SEM and the density of dislocations was estimated. In addition, HVPE growth of low dislocation density, high quality GaN, the properties of dislocations and the related physical issues and technique problems met in our research were also discussed. Together with the help of laser lift-off (LLO) process and growth techniques, the thick free-standing GaN films were obtained.