Plasma-assisted molecular-beam epitaxy of ZnO epilayers on atomically flat MgAl2O4(111) substrates

Plasma-assisted molecular-beam epitaxy of ZnO epilayers on MgAl2O4(111) substrates is described. Acid mixed by H2SO4 and H3PO4 was used for the substrate etching, which provides atomically flat surfaces with a regular terrace array. The influence of the substrate on lateral growth and coalescence of ZnO islands during epitaxy is discussed with corresponding morphological and structural properties. The epitaxial relationship between the ZnO epilayer and MgAl2O4 substrate is determined as: ZnO[01(1) over bar 0]parallel to MgAl2O4[<(11)over bar>2] and ZnO[<2(11)over bar>0]parallel to MgAl2O4[(1) over bar 10]. X-ray diffraction, photoluminescence, and Hall-effect measurements are reported, which indicate that high-quality ZnO epilayers are obtained by using atomically flat MgAl2O4(111) substrates to suppress columnar growth. (C) 2000 American Institute of Physics. [S0003-6951(00)01902-1].