Effect of band structure on Stark shifts in GaAs quantum wells

We have carried out a pseudopotential calculation of Stark effect on electron states in GaAs-${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Al}}_{\mathrm{x}}$As quantum-well structures. We find that in isolated wells the band-structure effect due to field-induced mixing of bulk Γ and X states is negligible in electric fields (0–5)×${10}^5$ V/cm. However, in double-barrier structures normally used to study resonant tunneling the effect of Γ-X mixing drastically reduces the magnitude of critical field, at which quadratic Stark effect and the particle-in-a-box model collapse, to around 2×${10}^5$ V/cm. We predict that this critical field is also a sensitive measure of the interface quality.