TEM study of RTD structure fabricated with epi-Si/γ-Al2O3 heterostructure

Fabrication of γ-Al2O3/epi-Si/γ-Al2O3/Si-sub resonant tunneling diode structure has been performed and interfacial and crystalline quality of the fabricated RTD structure were characterized by high resolution transmission electron microscopy. Multiple layer structure formation with atomically flat interfaces was confirmed. The γ-Al2O3 layer on Si-sub was observed highly crystalline and oriented along the orientation of the Si substrate. But the epi-Si layer was not smoothly crystalline over the whole specimen and also crystallinity varies from place to place. The epitaxial Si layer was observed to be strained due to the difference in thermal expansion coefficient and the lattice mismatch between γ-Al2O3 and silicon.