Structural and Photoluminescence Properties of ZnO Films Grown on 6H-SiC Substrates by Low-Temperature Atomic Layer Deposition

Abstract

We have applied atomic layer deposition (ALD) technique to grow high-quality ZnO films on 6H-SiC substrates at low temperature. The columnar growth with c axis normal to the substrate surface occurred in the ZnO films grown at temperatures above 270°C. The crystalline quality was improved by post-deposition annealing at 650°C. However, no preferred orientation growth was observed in the ZnO films deposited at a low temperature of 180°C, even after the post-annealing treatment. A two-step approach was developed to prepare high-quality and highly orientated ZnO films at a low deposition temperature of 180°C, by introducing ZnO buffer layer grown at a high temperature of 300°C. Optically pumped stimulated emission in the ZnO films with a high threshold intensity of 750 kW/cm2 was observed at room temperature, indicating that both the carrier and optical confinement are important to achieve the low-threshold stimulated emission in ZnO films.