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

Growth of ZnSnN 2 films on (0001) Al 2 O 3 substrates is performed by plasma-assisted molecular-beam epitaxy by changing the growth temperatures from 350 to 650 °C. Single crystal ZnSnN 2 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 ZnSnN 2 films with ZnO buffer show a pseudowurtzite structure without the formation of an orthorhombic structure. Epitaxial relationships between Al 2 O 3 substrate, ZnO buffer, and ZnSnN 2 film are determined to be [112̅0] ZnSnN 2 //[112̅0] ZnO//[101̅0] Al 2 O 3 and [0001] ZnSnN 2 //[0001] ZnO//[0001] Al 2 O 3 . The bandgaps of ZnSnN 2 films could be tuned from 1.85 to 2.15 eV, simply by increasing the growth temperatures from 350 to 650 °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 ZnSnN 2 films, which is needed to fabricate new ZnSnN 2 -based devices.