A multijunction solar cell comprising at least a first subcell and a second subcell, a first alpha layer disposed over said first solar subcell grown using a surfactant and dopant including selenium or tellurium, the first alpha layer configured to prevent threading dislocations from propagating; a metamorphic grading interlayer disposed over and directly adjacent to said first alpha layer; a second alpha layer grown using a surfactant and dopant including selenium or tellurium over and disposed directly adjacent to said grading interlayer to prevent threading dislocations from propagating; wherein the second solar subcell is disposed over said grading interlayer such that the second solar subcell is lattice mismatched with respect to the first solar subcell.