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 °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 [112̅0] ZnSnN2//[112̅0] ZnO//[101̅0] 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 °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.