High Growth Rate Metal-Organic Molecular Beam Epitaxy for the Fabrication of GaAs Space Solar Cells

Abstract

AbstractRealization of high quality GaAs photovoltaic materials and devices by Metal-organic Molecular Beam Epitaxy (MOMBE) with growth rates in excess of 3 microns/ hours 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) tunnel diodes and solar cells fabricated at growth rates in excess of 31µm/h exhibit performances comparable to state of the art and stress the potential of the high growth rate MOMBE as a reduced toxicity alternative for the production of Space 111-V solar cells.