Epitaxial ZnO Layer Growth on Si(111) Substrates with an Intermediate AlN Nucleation Layer by Methane-Based Chemical Vapor Deposition

The growth of high-quality single-crystalline zinc oxide (ZnO) layers on silicon (Si(111)) substrates with an intermediate aluminum nitride (AlN) nucleation layer was investigated. The ZnO layers were grown using a methane (CH4)-based chemical vapor deposition (CVD) growth process, while the AlN nucleation layers were grown by metal-organic vapor-phase epitaxy (MOVPE). We investigate the influence of nucleation layer thickness and growth temperature on the final ZnO layer quality and also vary the ZnO growth parameters to obtain smooth surfaces and the best crystal quality. The ZnO layers were extensively characterized by various methods such as atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), electron backscatter diffraction (EBSD), and scanning/transmission electron microscopy (SEM/TEM). We find that AlN nucleation layers grown at 1150 degrees C for 15 min yielded the best final ZnO layer quality with fully c oriented ZnO layers free of rotational domains. In HRXRD omega scans full width of half maximum (fwhm) values of about 710 and 1240 arcsec for the (0002) and (10 (1) over bar2) reflections, respectively, were achieved. Dislocation densities of rho(edge) = 1.6 x 10(10) and rho(screw) = 9.1 x 10(8) cm(-2) and a lateral coherence length (LCL) of L-parallel to = 300 nm are deduced, values which are among the best reported in the literature for ZnO layers grown on Si(111). Additionally, we carried out high-resolution photoluminescence (PL) measurements at liquid-helium and room temperatures, which also prove low defect densities. The low-temperature PL spectra were also used to study the stress within the ZnO layer and compared to HRXRD stress measurements. Both measurements confirm a stress reduction in the ZnO layer with increasing thickness.