Optical absorption and photovoltaic spectra induced by exciton resonance in GaAs/GaAlAs multiple quantum well

Optical absorption and photovoltaic spectra of GaAs/GaAlAs MQW structures, previous measured, are discussed. The thermal broadening of the absorption peaks related to n = 1 exciton states is explained in the light of interaction with the two types thermal phonons (LO in GaAs and new due to an inhomogeneity near the well-barrier interface). The energy of new phonons for two different MQW structures is fitted as E1 = 30 MeV and E2 = 16 MeV. The intensity of the photovoltaic peaks showed non-monotonic behaviour with minimum at about 100 K. This minimum is explained as a consequence the maximum of the exciton lifetime in the same region of temperature for these MQW structures. (author)