Monolithically integrated high-efficiency multijunction solar cells are highly desirable for both space and terrestrial applications. This paper reports recent experimental work on newly proposed multijunction solar cell designs that utilize lattice-matched II/VI CdZnSeTe and III/V AlGaAsSb materials grown on GaSb substrates. Single ZnTe layers and thin CdZnTe/ZnTe quantum wells have been grown on GaSb substrates using molecular beam epitaxy. Reflection high-energy electron diffraction, high-resolution x-ray diffraction, and photoluminescence at various temperatures up to room temperature have been carried out to study these samples. These measurements show that excellent crystalline and optical quality can be realized in the integration of these materials.