Detection of Defect Activated Phonon Modes in Subband Transitions of GaAs–AlGaAs Quantum Well Structures

Inter-subband excitations and contributions of defect-induced phonon modes for undoped GaAs–AlGaAs quantum well structures were examined by using Fourier Transform Spectroscopy. Transitions corresponding to n 1 – n 2 for 70 Å, 110 Å and 160 Å as well as higher transitions for 110 Å and 160 Å well widths were identified. The obtained values are in good agreement with the computed ones for the barrier heights 262 meV and m * =0.063 m 0 . It is found that inter subband transitions are assisted by the combination of defect-activated modes corresponding to TO (DATO) and LO (DALO) phonons. The values obtained in the present investigation are in good agreement with the earlier reported studies.