Effect of Buffer Temperature on Epilayer Morphology for GaN on Si(111)

GaN epitaxial layers were grown on Si(111) substrates with AlN buffer layers at different growth temperature. X-ray diffraction(DCXRD) and scanning electron microscope(SEM) were used as analysis tool to reveal the relation between growth temperature of buffer layer and epilayer surface morphology. The “pits” on epitaxial surface and the relation with buffer growth temperature were explained through these analysis.It indicates that the buffer growth temperature influences surface morphology through nucleation seed density and dimension dropped on the Si(111) substrate at initial time of buffer growth. When the buffer temperature was low, nucleation seeds were frozen on the surface of substrate and could not move to neighboring seeds. Nucleation seeds density was high and dimension was small. When the buffer temperature was high, the nucleation seeds had enough energy to merge with other seeds and density of seeds was low and dimension was big. This nucleation difference caused the epilayer morphology difference. Through this analysis, one growth model was created to guide the later experiments.