Improved vertically stacked Si/SiGe resonant interband tunnel diode pair with small peak voltage shift and unequal peak currents

A vertically integrated and serially connected npnp Si-based resonant interband tunnelling diode (RITD) pair is realised with low temperature molecular beam epitaxy (MBE) by monolithically stacking two RITDs with different spacer thicknesses. The asymmetric design manifests as unequal peak current densities that provide for much larger and uniform separation of the holding states for multi-valued logic. A δ-doped backwards diode connects the two serially connected RITDs with a very small series resistance. The I-V characteristic of the improved vertically integrated RITDs demonstrates two negative differential resistance (NDR) regions in the forward biasing condition with a small peak shift and unequal peak currents.