Intersubband transitions for differently shaped quantum wells under an applied electric field

Calculations were made to compare the Stark shifts of electron intersubband transitions in Al_0.4Ga_0.6As/Al_xGa_1-xAs quantum wells. Several differently shaped quantum wells, having the same subband spacing between the ground and first excited states, E₂₁=124 meV (=10 μm) under zero bias, were considered. The asymmetric steplike wells showed larger intersubband Stark shifts and a relatively high oscillator strength as well as a small linewidth broadening. A linear intersubband Stark shift of ±10 meV for ±100 kV/cm with a moderate change of the oscillator strength was found for an asymmetric well with its potential shape intermediate between a square and an asymmetric triangular one.