Well-width dependence of bound to quasi-bound intersubband transition in GaAs quantum wells with multi-quantum barriers

Well-width dependence of bound to quasi-bound intersubband transitions in GaAs quantum wells (QW) with multi-quantum barriers (MQB) is investigated. Narrowing the well width, the absorption peak shifts to higher energy while integrated absorption intensity decreases as the quasi-bound state energy increases. The transition energies are in good agreement with the calculation, whereas the observed decrease of integrated absorption is found to be larger than the decrease in oscillotor strength due to the spread to quasi-bound wave function. Using a simple rate equation, the decrease of the integrated absorption is discussed.