NOVELTY - A semiconductor structure (100) comprises, indium-phosphorus (InP) substrate (101); optional indium-gallium-arsenide-phosphorus (InGaAsP) building block formed over and lattice matched/pseudomorphically strained to substrate; indium-phosphorus (InP) building block (102) formed over and lattice matched/pseudomorphically strained to either InGaAsP building block or InP substrate; (zinc-cadmium-mercury)(selenium-tellurium) (ZnCdHg)(SeTe) building block (103) formed over and lattice matched/pseudomorphically strained to InP building block; and tunnel diode between each of building blocks.    USE - As semiconductor structure used in a solar cell (claimed).    ADVANTAGE - The use of lattice-matched materials eliminate misfit dislocations that reduce material quality; the use of direct bandgap materials maximize the absorption and minimizes the thickness of the junction region to minimize series resistance, material usage and growth time. It optimizes the overall conversion efficiency of the whole device. It minimizes the series resistance of the contacts, the tunnel diodes, contact layers, and the substrate; and decreases the efficiency reduction from the loss of solar radiation below the lowest bandgap energy of present devices.    DETAILED DESCRIPTION - A semiconductor structure (100) comprises, an indium-phosphorus (InP) substrate (101); an optional indium-gallium-arsenide-phosphorus (InGaAsP) building block formed over and lattice matched or pseudomorphically strained to the InP substrate; an InP building block (102) formed over and lattice matched or pseudomorphically strained to either (i) the InGaAsP building block, when present; or (ii) the InP substrate; at least one (zinc-cadmium-mercury)(selenium-tellurium) (ZnCdHg)(SeTe) building block (103) formed over and lattice matched or pseudomorphically strained to the InP building block, where, when more than one (ZnCdHg)(SeTe) building block is present, each (ZnCdHg)(SeTe) building block has a different bandgap; and a tunnel diode between each of the building blocks.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of semiconductor structure.    Semiconductor structure (100)    Indium-phosphorus substrate (101)    Indium-phosphorus building block (102)    Zinc-cadmium-mercury-selenium-tellurium building block building block (103)