Optical properties of miniband formed in the InGaAs/GaAs quantum well solar cells by means of photoreflectance, photoluminescence, and photothermal spectroscopies

To investigate the miniband and carrier transport properties in the superlattice structure embedded in the p-i-n GaAs solar cells, photoreflectance, photoluminescence, and photothermal spectroscopies were adopted. Two critical energies corresponding to the energy differences between mini-Brillouin zone edges were estimated for thinnest quantum barrier thickness sample by PR. From the PPT and PL, only broad peaks corresponding to the quantum levels were observed and we concluded that a built-in electric field inhibited the formation of miniband.