p-GaAs substrate was used as the starting material in molecular beam epitaxial growth. n-type GaAlAs for heterostructure and n-GaAs capping layer were then grown after a buffer layer deposition on the substrate. The n-GaAlAs on p-GaAs heterostructure solar cells, with active area of 13.25 mm(2) under 100 mW/cm(2) AM 1 illumination light source, provide a typical output as follows: V-OC = 0.73 V, I-SC = 6 mA, FF - 0.7 and eta = 23% (active area). Spectral response measurements from 500 to 850 nm reflects the window effect of GaAlAs and band edge of GaAs materials. (c) 2006 Elsevier B.V. All rights reserved.