Effects of interruption growth on the properties of ZnO active layers grown by using plasma-assisted molecular beam epitaxy

ZnO active layers were grown on Si (100) substrates by using plasma-assisted molecular beam epitaxy (PA-MBE). The initial regions of the ZnO active layers were deposited by using an interruption growth method (IGM), with the following ZnO active layers being grown in succession for 80 min without interruption. X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements were carried out to investigate the structural and the optical properties of the ZnO active layers. The full width at half maximum (FWHM) of the rocking curve observed for the ZnO (002) XRD peak decreased from 0.191° to 0.176° and the intensity of the XRD peak increased with increasing Zn beam ON time. The surface morphology shows a net-like structure that changes with the Zn beam ON time. The PL intensity of the near-band-edge emission (NBE) peak is enhanced in the ZnO active layers grown on interrupted layers, and the NBE peak position is blue-shifted with increasing Zn beam ON time, which was caused by an enhancement of the tensile stress. The above results imply that the IGM is effective in improving the crystalline quality and the luminescence efficiency.