Cubic Zn_xMg_(1-x) O thin films grown by plasma-assisted molecular-beam epitaxy for optoelectronic applications

摘要

Heteroepitaxial Zn_xMg_(1-x) O thin films were grown on lattice-matched MgO (100) substrates using radiofrequency plasma-assisted molecular-beam epitaxy. High-quality epilayers with zinc concentrations ranging from x = 0 (MgO) to x = 0.65 were grown and characterized optically, structurally, and electrically. The Zn_xMg_(1-x)O films were found to maintain the rocksalt cubic (B1) crystal structure for concentrations z < 0.65, with a linear dependence of lattice constant on Zn concentration. X-ray diffraction (XRD) also revealed the emergence of phase segregation into wurtzite (B4) phase for the highest concentration film. The band gap energy of the films was successfully varied from 4.9 to 6.2 eV (253-200 nm), showing a linear relationship with Zn concentration. The strictly cubic films exhibit roughness on the order of 10 A and resistivities of approximately 10~6 Ω.cm.