MOVPE growth of AlGaN/GaN superlattices on ZnO substrates for green emitter applications

AlGaN/GaN superlattice structures have been deposited on (0 0 0 1) ZnO substrates by metalorganic vapor phase epitaxy. The growth conditions were first optimized on GaN templates using N2 as carrier gas at relatively low temperature (<800 °C), which is suitable for GaN growth on a ZnO substrate. Experimental results show that high interfacial quality can be achieved in the superlattice by using TMIn as a surfactant. The optimized growth conditions were subsequently transferred to ZnO substrates. The influence of growth temperature on the material quality was studied. A proper growth temperature for both GaN cover layer and AlGaN/GaN superlattice can improve the structural and optical properties of the structures on ZnO. This improvement is verified using X-ray diffraction, atomic force microscopy and photoluminescence characterizations. The growth temperature must be chosen with these two factors in mind, with too low a growth temperature leading to poor quality material and too high a temperature causing reactions at the GaN/ZnO interface that degrade quality.