Nonlinear absorption in n-i-p-i MQWs structure

The absorption coefficient of the n-i-p-i multi-quantum well(MQW) structure is calculated using an average dipole moment matrix element and variational method. Taking into account both of the excitonic binding energy and shift in absorption subband edge due to the quantum confined Stark effect(QCSE), modulation of the optical absorption spectrum of the structure due to illumination has been analyzed. The calculated absorption peaks arising from le-1hh and le-1lh transitions their changes under optical excitation agree well with the published data. It is found that the exciton peaks' positions are dependent on the bandgap offsets ratio of the quantum well structure. Shifts in the absorption peaks due to illumination is contributed mainly by QCSE, but the contribution due to the change in exciton binding energy is one order of magnitude lower.