Inhomogeneous strain relaxation in triple-barrier (formula presented) nanostructures

Resonant tunneling measurements are used to probe size-induced strain relaxation in p-Si/SiGe triple-barrier nanostructures with a narrow (∼10 Å) middle barrier, where the confined subbands depend strongly on the strain and bias-dependent coupling between the two neighboring quantum wells. In structures with (Formula presented) diameter, shifts in the strain-dependent subband energies are clearly observable in the tunneling current. Further, in the smallest structures (Formula presented) tunneling through discrete states confined by inhomogeneous-strain-induced lateral potentials dominates the (Formula presented) Magnetotunneling measurements on a (Formula presented) structure reveal a ∼75-Å effective length of the strain-induced lateral confinement potential. Based on our previous measurements of double-barrier nanostructures and the finite element calculations of the strain distribution in these triple-barrier structures, we conclude that the (Formula presented) peak shifts in larger devices are due to uniform strain relaxation, whereas in smaller devices the fine structure in the (Formula presented) is due to coupled inhomogeneous-strain-induced discrete quantum-dot or ring states in neighboring wells. © 1999 The American Physical Society.