Described herein are semiconductor structures comprising laterally varying II-VI alloy layer formed over a surface of a substrate. Further, methods are provided for preparing laterally varying II-VI alloy layers over at least a portion of a surface of a substrate comprising contacting at least a portion of a surface of a substrate within a reaction zone with a chemical vapor under suitable reaction conditions to form a laterally varying II-VI alloy layer over the portion of the surface of the substrate, wherein the chemical vapor is generated by heating at least two II-VI binary compounds; and the reaction zone has a temperature gradient of at least 50-100 C. along an extent of the reaction zone. Also described here are devices such as lasers, light emitting diodes, detectors, or solar cells that can use such semiconductor structures. In the case of lasers, spatially varying wavelength can be realized while in the case of solar cells and detectors multiple solar cells can be achieved laterally where each cell absorbs solar energy of a given wavelength range such that entire solar spectrum can be covered by the said solar cell structure. For LED applications, spatial variation of alloy composition can be used to engineer colors of light emission.

In some embodiments, a semiconductor structure includes a single crystal substrate, a first epitaxial oxide layer on the single crystal substrate, and a second epitaxial oxide layer on the single crystal substrate. The first epitaxial oxide layer can include a first oxide material with a cubic crystal symmetry. The second epitaxial oxide layer can include a second oxide material with a monoclinic crystal symmetry. The second epitaxial oxide layer can be elastically strained to the first epitaxial oxide layer. The substrate can include MgO, MgAl.sub.2O.sub.4, or -Ga.sub.2O.sub.3. The first epitaxial oxide layer can include MgO with a cubic crystal symmetry oriented in the (100) direction, and the second epitaxial oxide layer can include -Ga.sub.2O.sub.3 oriented in the (100) direction, where there is a 45 rotation around the (100) direction between the MgO and the -Ga.sub.2O.sub.3 crystal structures.