Preparation and characterization of ZnO film on Si(111) substrate with SiC buffer layer deposited by MOCVD

Recently, ZnO has attracted great attention due to its ultraviolet luminescence. In order to fabricate high-efficiency light emitting devices, good quality single crystal ZnO films are required. Since the ZnO single crystal wafers are too expensive, most ZnO films were prepared by hetero-epitaxy. Si substrate is a powerful candidate for the ZnO hetero-epitaxy due to not only its low cost, but also the additional advantages in photoelectric integration. However, it is difficult to get high quality ZnO single crystal films on Si substrates because of the large lattice mismatch between ZnO and Si.. In these experiments, a special low-pressure metal-organic chemical vapor deposition system has been designed, which has two reactors connected each other by a gate valve. Using this equipment, highly c-axis oriented ZnO epitaxial films were deposited on Si (111) substrate by though a SiC buffer layer in order to reduce the lattice mismatch between ZnO and Si. The SiC buffer layers and the ZnO films were prepared in different reactor of the special MOCVD system. It can prevent the pollution between SiC and ZnO during growth. The measurement of Fourier-transform infrared absorption spectra (FTIR) and double-crystal X-ray diffraction indicate that the SiC film is 3C phase and the rocking curve FWHM of SiC (111) is 0.6°.For the ZnO grown on Si(111) substrate with a 3C-SiC buffer layer, he rocking curve FWHM of ZnO(002) is 1.19°, much lower than that of the ZnO film directly grown on Si substrate. These experimental results prove that the SiC buffer layer is useful for modulating the lattice mismatch between ZnO and Si. Using a lattice-matched mode between Si, SiC and ZnO supposed here, the influnce of SiC buffer layer can be explained very well. The photoelectric properties of ZnO/SiC/Si materials were also greatly improved by SiC buffer layer. Much stronger ultraviolet emission has been observed in the photoluminescence spectra at room temperature. Moreover, the photovoltaic effect has also been enhanced, and it exhibited a novel stepped special response.