Epitaxial growth of Mg_xCa_(1-x)O on 4H-SiC(0001) and β-Ga_2O_3(201) wide band gap semiconductors with atomic layer deposition

摘要

SiC and Ga_2O_3 are promising wide band gap semiconductors for applications in power electronics because of their high breakdown electric field and normally off operation. However, lack of a suitable dielectric material that can provide high interfacial quality remains a problem. This can potentially lead to high leakage current and conducting loss. In this work, we present a novel atomic layer deposition process to grow epitaxially Mg_xCa_(1-x)O dielectric layers on 4H-SiC(0001) and β-Ga_2O_3(201) substrates. By tuning the composition of Mg_xCa_(1-x)O toward the substrate lattice constant, better interfacial epitaxy can be achieved. The interfacial and epitaxy qualities were investigated and confirmed by cross-sectional transmission electron microscopy and X-ray diffraction studies. Mg_(0.72)Ca_(0.28)O film showed the highest epitaxy quality on 4H-SiC(0001) because of its closest lattice match with the substrate. Meanwhile, highly textured Mg_(0.25)Ca_(0.75)O films can be grown on β-Ga_2O_3(201) with a preferred orientation of (111).