Integration of Zn-Cd-Te-Se Semiconductors on Si platforms via structurally designed cubic templates based on group IV elements

This work describes the development and application of a new class of highly versatile Ge-Sn/Si (100) hybrid substrate systems for the integration of a broad range of technologically important II-VI optical materials on silicon platforms. GeSn buffer layers were grown directly on Si(100), via introduction of Lomer edge dislocations at the interface, and exhibited low densities of threading defects, atomically flat surfaces, and strain-free microstructures. Specialized cleaning protocols were first developed to obtain GeSn surfaces possessing superior chemical purity and single-crystalline, long-range orientation for subsequent heteroepitaxy. The quality of the resulting platforms was then validated using proof-of-concept fabrication of prototype AlGaAs/GaAs/AlGaAs quantum well structures, which exhibited optical properties comparable to those of analogs grown via homoepitaxy on bulk GaAs substrates. The application of these platforms in CMOS-compatible integration of the II-VI materials was explored using a progressive strategy based on the systematic epitaxial fabrication of simple binaries within Zn-Cd-Te-Se class. This culminated in the formation of fully lattice matched ZnSe/GeSn/Si(100) structures for the first time, as well as highly mismatched CdTe and CdTe/ZnTe systems directly on silicon. These successful depositions represent an importantmilestone en route to the ultimate integration of ZnSe, CdTe, Zn _1-zCd _zTe andHg _1-xCd _xTe with Si for applications in high-performance IR photodetectors, imaging technologies, and highefficiency, low-cost solar cells.