A semiconductor structure for a multijunction solar cell comprising: a first semiconductor layer having a first bandgap and a first lattice constant; a second semiconductor layer having a second bandgap and a second lattice constant, the second lattice constant being lower than the first lattice constant; and a transparent metamorphic buffer layer disposed between the first semiconductor layer and the second semiconductor layer, the buffer layer having a varying lattice constant, the varying lattice constant being matched to the first lattice constant adjacent the first semiconductor layer and matched to the second lattice constant adjacent the second semiconductor layer, wherein the buffer layer comprises a first portion having a constant or substantially constant bandgap and comprising Al y Ga z In (1-y-z) As and a second portion comprising Ga x In (1-x) P, the first portion being adjacent the first semiconductor layer and forming between about 2 percent and about 50 percent of the total thickness of the buffer layer, and the second portion being adjacent the second semiconductor layer and forming between about 50 percent and about 98 percent of the total thickness of the buffer layer, and the first portion of the buffer layer comprises a plurality of compositionally graded steps (1311, 1312, 1313, 1314) comprising Al y Ga z In (1-y-z) As and the second portion of the buffer layer comprises a plurality of compositionally graded steps (1321, 1322, 1323, 1324) comprising Ga x In (1-x) P, wherein one of the plurality of Al y Ga z In (1-y-z) As steps is immediately adjacent one of the plurality of Ga x In (1-x) P steps, the immediately adjacent Al y Ga z In (1-y-z) As and Ga x In (1-x) P steps having the same lattice constant. a first semiconductor layer having a first bandgap and a first lattice constant; a second semiconductor layer having a second bandgap and a second lattice constant, the second lattice constant being lower than the first lattice constant; and a transparent metamorphic buffer layer disposed between the first semiconductor layer and the second semiconductor layer, the buffer layer having a varying lattice constant, the varying lattice constant being matched to the first lattice constant adjacent the first semiconductor layer and matched to the second lattice constant adjacent the second semiconductor layer, wherein the buffer layer comprises a first portion having a constant or substantially constant bandgap and comprising Al y Ga z In (1-y-z) As and a second portion comprising Ga x In (1-x) P, the first portion being adjacent the first semiconductor layer and forming between about 2 percent and about 50 percent of the total thickness of the buffer layer, and the second portion being adjacent the second semiconductor layer and forming between about 50 percent and about 98 percent of the total thickness of the buffer layer, and the first portion of the buffer layer comprises a plurality of compositionally graded steps (1311, 1312, 1313, 1314) comprising Al y Ga z In (1-y-z) As and the second portion of the buffer layer comprises a plurality of compositionally graded steps (1321, 1322, 1323, 1324) comprising Ga x In (1-x) P, wherein one of the plurality of Al y Ga z In (1-y-z) As steps is immediately adjacent one of the plurality of Ga x In (1-x) P steps, the immediately adjacent Al y Ga z In (1-y-z) As and Ga x In (1-x) P steps having the same lattice constant.