Development of GaAs space solar cells by high growth rate MOMBE/CBE

Abstract

Realization of high-quality GaAs photovoltaic materials and devices by metalorganic molecular beam epitaxy (MOMBE) and chemical beam epitaxy (CBE) with growth rates in excess of 3 μm/h is demonstrated. Despite high growth rates, the optimization of III/V flux-ratio and growth temperatures leads to a two-dimensional layer-by-layer growth mode characterized by a (2×4) RHEED diagrams and strong intensity oscillations. The not intentionally doped layers exhibit low background impurity concentrations and good luminescence properties. Both n (Si) and p (Be) doping studies in the range of concentrations necessary for photovoltaic device generation are reported. Preliminary GaAs (p/n) solar cells fabricated at growth rates in excess of 3 μm/h exhibit performances comparable to state of the art and stress the potential of the high growth rate MOMBE/CBE as reduced toxicity alternatives for the production of space III–V solar cells.