DETECTION OF DEFECT ACTIVATED PHONON MODES IN SUBBAND TRANSITIONS OF GAAS-ALGAAS QUANTUM-WELL STRUCTURES

Inter-subband excitations and contributions of defect-induced phonon m odes for undoped GaAs-AlGaAs quantum well structures were examined by using Fourier Transform Spectroscopy. Transitions corresponding to n1- n2 for 70 angstrom, 110 angstrom and 160 angstrom as well as higher tr ansitions for 110 angstrom and 160 angstrom well widths were identifie d. The obtained values are in good agreement with the computed ones fo r the barrier heights 262 meV and m = 0.063m0. It is found that inter subband transitions are assisted by the combination of defect-activat ed modes corresponding to TO (DATO) and LO (DALO) phonons. The values obtained in the present investigation are in good agreement with the e arlier reported studies.