Study on RF-ZnO Buffer of GaN Film on Si(Ⅲ) Substrate

摘要

ZnO buffer layer and low-temperature GaN (LT-GaN) interlayer can reduce the lattice mismatch and coefficient of thermal expansion mismatch between GaN epitaxial layer and Si(111) substrate effectively. ZnO buffer has been fabricated by using radiofrequency (RF) magnetron sputtering on the basis of the optimal process conditions as follows: the background vacuum is 6.0×10-4Pa; the pressure of Ar gas is 1.5Pa; the sputtering power is 60W and the heating temperature of Si(111) substrate is at 200°C. The full width at half maximum of ZnO layer gets 794 arcsec, the crystal orientation emerges only (0002) crystallographic direction and the roughness is just 1nm. The GaN film made from LT-GaN/RF-ZnO/Si (111) composite substrate is crack-free and its surface appears smooth. Weak yellow emission and strong band edge emission appears in PL spectra of GaN film.