An investigation was made of the trapping mechanisms that were responsible for the persistent photo-effect in heavily doped GaAs/Ga0.7Al0.3As multiple quantum-well structures. A red shift in the inter sub-band transition energy, that was observed upon using secondary illumination, indicated a decrease in the carrier concentration of the wells; due to trapping in the barrier. A decrease was found in the strength of the persistent photo-effect when the energy of the photons from secondary illumination was below the band gap of Si (1.172eV). This observation was consistent with the existence of optically activated traps whose activation energy was greater than 1.172eV. These data, together with thermal recovery data, made the DX center the most probable candidate for the observed trap.

A.Gannon, D.Donnelly, B.Covington: Journal of Applied Physics, 1996, 79[9], 7169-72