Epitaxial lift-off GaAs solar cell from a reusable GaAs substrate

Modifications to the existing epitaxial lift-off(ELO) method are described, which enable lift-off of large area devices (like solar cells). With the modified ELO method crack-free III-V films were obtained, up to 2 inch, in diameter and 1-6 mu m thick. For the first time epitaxial lift-on GaAs solar cells were made which contained an etch sensitive Al0.85Ga0.15As window layer. An energy conversion efficiency of 9.9% (AMI1.5Gx1) was measured for the ELO GaAs cells. Compared to the thick GaAs reference cell, ELO cells still suffer from a low fill factor due to series and shunt resistances. Current GaAs ELO cells represent a power to weight ratio of 200 W kg(-1). Because of the high selectivity of the ELO method, GaAs substrates remain unaffected after ELO. Reuse of a GaAs substrate after ELO was investigated in order to reduce the cost of III-V solar cell modules. With a simple cleaning procedure, GaAs substrates could be used at least four times without degradation of the minority carrier lifetime or carrier mobility of the grown epilayers. (C) 1997 Elsevier Science S.A.