NOVELTY - Formation of multifunction solar cell comprises providing a first substrate (101) for epitaxial growth of semiconductor material, forming an upper first solar subcell on first substrate having a first band gap, forming a middle second solar subcell over first solar subcell, forming a graded interlayer over second solar cell, forming a lower third solar subcell over graded interlayer having a fourth band gap smaller than the second band gap such that third subcell is lattice mismatched with respect to second subcell, and forming a contact.    USE - Formation of multifunction solar cell (claimed).    ADVANTAGE - Since surface topography affects the bulk properties of semiconductor material as it grows and the layer becomes thicker, the use of surfactants minimizes threading dislocations in active regions; thus improving overall solar cell efficiency. The arsenide-based semiconductor material is much easier to process in standard commercial metalorganic chemical vapor deposition reactors, while the small amount of aluminum assures radiation transparency of metamorphic layers (116).    DETAILED DESCRIPTION - Formation of multifunction solar cell comprises:    (A) providing a first substrate (101) for epitaxial growth of semiconductor material, forming an upper first solar subcell on first substrate having a first band gap, and forming a middle second solar subcell over first solar subcell having a second band gap smaller than the first band gap;    (B) forming a graded interlayer over second solar cell, and forming a lower third solar subcell over graded interlayer having a fourth band gap smaller than the second band gap such that third subcell is lattice mismatched with respect to second subcell; and    (C) forming a contact having a contact resistance of less than 2x 10-4 ohms-cm2 over first subcell at less than or equal to 210 degrees C.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of a solar cell after deposition of semiconductor layers on growth substrate.    Substrate (101)    Barrier layers (115, 117)    Metamorphic layer (116)    Window layer (118)    P-type base layer (120)