Lateral epitaxial overgrowth of ZnO layers on hexagonally patterned buffer layers in low-temperature aqueous solution

Abstract

Abstract In conjunction with lift-off patterning and thermal annealing, we have fabricated hexagonal arrays of epitaxial ZnAl2O4 buffer layers on sapphire substrates. Taking advantage of the small lattice mismatch between ZnO (0001) and ZnAl2O4 (111), site-controlled epitaxial growth of ZnO prisms occurred on the pre-patterned, lattice-matched buffer layers. Subsequently, using a continuous flow reactor, long-duration maskless lateral epitaxial overgrowth (LEO) of ZnO prisms led to coalescence into continuous, thick layers within aqueous solutions at low temperature. X-ray diffraction (XRD) confirmed that LEO on the hexagonally patterned buffer layers facilitated the fabrication of strain-relieved, wing-tilt-free, thick ZnO layers. The dislocation density at the coalesced LEO-grown ZnO layer was approximately 108 cm−2. The spatial variation in the micro-photoluminescence characteristics of the LEO-grown layer suggested that the improvement in crystalline quality occurred in the overgrown wings, originating from the decrease in dislocation in the ZnO layer during the LEO process.