Epitaxial Growth of Bandgap Tunable ZnSnN2 Films on (0001) Al2O3 Substrates by Using a ZnO Buffer

Growth of ZnSnN2 films on (0001) Al2O3 substrates is performed by plasma-assisted molecular-beam epitaxy by changing the growth temperatures from 350 to 650 degrees C. Single crystal ZnSnN2 films have been grown by using ZnO buffer while the film grown without the ZnO buffer has shown amorphous-like disordered characteristics addressed by no observation of any diffraction from reflection high-energy electron diffraction. All the grown crystalline ZnSnN2 films with ZnO buffer show a pseudowurtzite structure without the formation of an orthorhombic structure. Epitaxial relationships between Al2O3 substrate, ZnO buffer, and ZnSnN2 film are determined to be [11 (2) over bar0] ZnSnN2//[11 (2) over bar0] ZnO//[10 (1) over bar0] Al2O3 and [0001] ZnSnN2//[0001] ZnO//[0001] Al2O3. The bandgaps of ZnSnN2 films could be tuned from 1.85 to 2.15 eV, simply by increasing the growth temperatures from 350 to 650 degrees C. The carrier concentrations and carrier mobilities were investigated and compared. Since the growth of single crystal ZnO films has been reported on various kinds of cheap and large size substrates, our results can expand the method to grow single crystal ZnSnN2 films, which is needed to fabricate new ZnSnN2-based devices.