High performance of multi-quantum well (MQW) solar cells depends not only on the material quality ensuring minimum non-radiative recombination losses expected at the heterointerfaces, but also on the escape rate of photogenerated carriers out of QWs with minimum radiative losses within QWs. We investigated potentially modulated MQW solar cell structures, for which the MQW structure is modified from a series of conventional square-shaped QWs to "step-like" potentially modulated QWs. We fabricated "two-step" and "three-step" MQWs introduced into the intrinsic region of GaAs p-i-n solar cells by atomic H-assisted molecular beam epitaxy (H-MBE). Compared with a square-shaped MQW cell, a three-step modulated MQW cell having the same average potential well depth showed photoluminescence characteristics with a smaller thermal activation energy and higher average carrier temperature and indicated that photogenerated carriers escape out of QWs more efficiently in this type of structure. (C) 2004 Elsevier B.V. All rights reserved.