Strain relaxation in silicon‐germanium microstructures observed by resonant tunneling spectroscopy

We have measured the resonant tunneling current–voltage I(V) characteristics of strained p‐Si/Si1−xGex double‐barrier microstructures ranging from 1.0 to 0.1 μm in lateral extent. The bias spacing between resonant current peaks in the I(V) reflects the energy separation of the Si1−xGex quantum well subbands, which is partially determined by the strain. As the lateral size of the structures decreases, we observe consistent shifts in the I(V) peak spacing corresponding to strain energy relaxation of ∼30% in smaller structures. An additional I(V) fine structure is observed in the 0.1 μm device, consistent with lateral quantization due to nonuniform strain.