Resonant Tunneling Diodes in Si/CaF 2 Heterostructures Grown by Molecular Beam Epitaxy

Room-temperature negative differential resistance (NDR) was observed in Si/CaF2 double-barrier resonant tunneling diodes fabricated by molecular beam epitaxy with annealing. The devices consist of Au/CaF2(amorphous)/Si(amorphous)/CaF2 (crystalline)/n+-Si(111)(substrate). In spite of the fact that the well layer (Si) and one of the barrier layers (CaF2) were amorphous, their interface was well distinguished in a transmission electron microscope image, and clear NDR was obtained with the peak-to-valley current ratio of 3.10 for a sample with a 2.8-nm-thick Si well. The voltage at the peak current varies with the thickness of the Si well, as predicted theoretically.