Resonant tunneling diodes made up of stacked self-assembled Ge/Si islands

Multiple layers of self-assembled Ge/Si islands are used for resonant tunneling diodes (RTDs). The extremely closely stacked Ge nanostructures form vertical channels with energetically deep thermalization layers and high Si double barriers. Two resonances are found in the RTD current–voltage curve, which are attributed to the heavy-heavy hole (hh) and heavy-light hole (lh) transition. The lh resonance shows negative differential resistance up to 50 K. With increasing magnetic field, the lh resonance slightly shifts to higher voltages.