Strain dependence of piezoelectric coefficients for pseudomorphically grown semiconductors

Advances in nanofabrication techniques have opened a plethora of opportunities to exploit the electrical and optical properties of exotic nanostructures such as Quantum Dots. Internal strain in such nanostructures facilitates band engineering. In this work we focus on III-As materials (GaAs/InAs) to study the strain dependence on the piezoelectric coefficients. The piezoelectric effect in quantum dots is one of the main sources of electronic anisotropy and as such has very important consequences over the symmetry and degeneracy of the energy levels. We find that strain in such nanostructures modifies the value of the piezoelectric coefficients to the extent of inverting the polarization compared to the bulk case. Consequently the piezoelectric potential alters the band dynamics of carriers trapped in such structures and has important consequences for the electronic and optical performance. For the case of InAs pseudomorphically grown on GaAs substrate, our model predicts a sign reversal of the piezoelectric coefficients e₁₄, e₂₅ and e₃₆ from negative to positive. This finally explains several discrepancies between the theoretical and experimental observations (anisotropy in p-levels) made on nanostructures such as III-V quantum dots.