HVPE Growth Of GaN For Homoepitaxial Growth

The growth of GaN is complicated due to the absence of a lattice matched bulk substrate. While bulk GaN is being pursued, substantial progress in growing high quality GaN by the hydride vapor phase epitaxy(HVPE) method has been achieved in recent years. High growth rates make the growth of thick layers practical. These thick layers have the potential to provide lattice matched and thermally matched quasi-bulk c-plane sapphire substrates are still highly defective compared to more common semiconductors. Therefore, how to reduce the dislocation density and further to improve the quality of GaN epi-layers are still exigent at present. In this paper we have made a study and analysis for HVPE method growing GaN . The main results are listed below: 1. We analyze carefully the advantage and disadvantage of HVPE methods. The GaN compliant substrate is developed in order to improve the quality of GaN epilayer. We designed the HVPE system and installed it for the large area GaN compliant substrate. laser lift off(LLO)can improve GaN quality according to thick layer and morphology. 2. The morphology characters of the GaN compliant substrate are studied. The defects such as, pits, cracks, macro-pyramids and leaf-like pattern of Ga droplets, were found by SEM and AFM. Some macro-pyramids have been found firstly on the surface of the sample. Macro-pyramid with the step height of 30--40nm was clearly observed through AFM. A simple model was proposed to explain the phenomenon of macro-pyramid growth. For the nucleation of macro-pyramid, the active energy ?Ecrit is calculated as 3.08 eV and the driving force Pcrit/P0 as 1.65 x 103. The growth of macro-pyramid is dependent on the physical conditions in the reactor cell. The GaN epilayers are of good quality according to the results of XRD, but it has the mosaic structure. 3. The growth front evolution of GaN thin films deposited on sapphire substrates by hydride vapor phase epitaxity has been studied with atomic force microscope. The evolution of the surface morphology presented four features of stage with the growth process:(1)in initial growth stage, the GaN growth is predominated by 3D growth...