Strain-induced electronic energy changes in multilayered InGaAs/GaAs quantum wire structures

Electronic states of layered InGaAs/GaAs(001) quantum wire and quantum dot chain structures have been investigated by electroreflectance and surface photovoltage spectroscopy. Band-gap shrinkage and heavy-hole/light-hole state splitting have been observed in the GaAs barrier material. This can be understood by shear strain existing in the GaAs barrier due to strain relaxation and anisotropy within the wires or dot chains. By comparing the experimental results with theoretical calculations, we found that the strain relaxation in the direction perpendicular to the wires or the dot chains has a stronger effect on the heavy-hole–light-hole splitting than on band-gap modification in the InGaAs wires and dot chains. The piezoelectric field induced by the shear strain is also discussed.