High-throughput synthesis and characterization of Mg1 xCaxO films as a lattice and valence-matched gate dielectric for ZnO based field effect transistors

Using composition-spread technique, we have grown metastable Mg1 xCaxO solid solution films on ZnO layers by pulsed laser deposition. All the films exhibited (1 1 1) oriented cubic phase. Despite a large miscibility gap, no phase separation took place at growth temperatures up to 700 8C, whereas an optimal growth temperature was found at 400 8C in terms of the crystallinity. The composition-spread films were characterized by X-ray diffraction mapping technique. Both lattice parameters and diffraction intensity increased with increasing the CaO composition. The present isovalent heterointerfaces realized the perfect lattice-matching by properly adjusting the CaO composition, leading to particular interest for ZnO based field effect transistors.