Development of an intermediate-temperature buffer layer for the growth of high-quality GaxInyAlzN epitaxial layers by molecular beam epitaxy

摘要

Gallium nitride and its related alloys have attracted much attention due to their important optoelectronic applications in blue to UV range as well as in the area of high-temperature electronics. Due to significant mismatches in the lattice constants and coefficients of thermal expansion between the GaN material and the sapphire substrate, GaN films typically exhibit large defect concentration and residual strain. In the present invention, a 20 nm thick low-temperature buffer layer is first grown on the sapphire substrate at preferably 500° C. This is followed by the growth of an intermediate-temperature GaN buffer layer (ITBL) at preferably 690° C. Finally, the epitaxial GaN layer is grown on top of the ITBL at preferably 750° C. It is found that the film quality is significantly affected by the use of an ITBL.