NOVELTY - The method involves providing a growth substrate (101) for epitaxial growth of semiconductor material. An upper solar subcell (A) with high band gap is formed on the substrate. A graded interlayer (116) is formed over a middle solar subcell (B) which is formed on the upper subcell. A lower solar subcell (C) with lower bandgap is formed over the interlayer, such that lower subcell is lattice mismatched with respect to the middle subcell. A surrogate substrate is attached over the lower subcell and the growth substrate is removed.    USE - Method of forming multi-junction solar cell for satellite and other space-related applications. Can also be used in thermo-photovoltaic cells, photodetector and LED.    ADVANTAGE - The short wavelength response for the middle and lower solar subcells is improved. The bulk of radiation is more effectively absorbed and collected in the narrower band gap base, so that the short circuit current is increased.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for manufacturing method of solar cell array. INORGANIC CHEMISTRY - The upper solar subcell is composed of gallium indium phosphide (GaInP), gallium arsenide (GaAs), gallium indium arsenide (GaInAs), gallium arsenide antimonide (GaAsSb), or gallium indium arsenide nitride (GaInAsN) emitter region, and an GaAs, GaInAs, GaAsSb, or GaInAsN base region, and the middle solar subcell is composed of an indium gallium arsenide (InGaAs) base and emitter regions. The transition material comprises indium-gallium-aluminum arsenide layers having a composition of formula: (InxGa1-y)yAl1-yAs, where x and y are chosen such that the band gap of each layer remains constant throughout the thickness of the transition material. METALLURGY - The contact metal layer is made of titanium (Ti), gold (Au), and silver (Ag). The transition material is made of arsenide (As), Phosphide (P), nitride (N) and antimony (Sb).    DESCRIPTION OF DRAWING(S) - The drawing shows a solar cell after the semiconductor layers on growth substrate.    Growth substrate (101)    Grade interlayer (116)    Upper solar subcell (A)    Middle solar subcell (B)    Lower solar subcell (C)