Misfit Dislocation Dynamics at Heterovalent Semiconductor Interfaces

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Non-Technical Description: As scientists and engineers seek to develop future generations of functional electronic and optical semiconductor devices - transistors, light emitting diodes, lasers, photodetectors, solar cells and beyond - integration of dissimilar, but complementary materials is a crucial step toward achieving new and desirable properties. However, these fundamental dissimilarities, or incompatibilities, tend to result in the formation of defects within the constituent semiconductor materials during the integration process, which detrimentally impacts the operation of the devices produced using these materials. Therefore, to enable the free and flexible application of dissimilar materials integration toward new device concepts, the various problems introduced by these incompatibilities must be understood and methods for their mitigation must be developed. This project seeks to better understand the impact and interplay between two common dissimilarities that exist in many target materials integration systems: heterovalency (dissimilar chemical bonding) and lattice mismatch (dissimilar atomic spacing). The results of this work are expected to provide guidance to researchers with respect to the design of fabrication processes that can avoid or minimize detrimental defect formation, making possible the development of next generation semiconductor devices with powerful new and beneficial properties. This project is also training graduate and undergraduate students as future innovators within the semiconductor research and development industry, while also establishing new research techniques and methods are benefit a wide range of investigators and enterprises within the field.Technical Description: The proposed work tackles important questions regarding the physical, chemical, and electronic structure of the heterovalent, lattice-mismatched interfaces and their impact on the formation and evolution of misfit dislocations within dissimilar materials integration systems. Understanding the specific relationships between dislocation dynamics and the underlying materials dissimilarities could enable bottom-up epitaxial and structural design approaches that allow for the control and mitigation of detrimental defect microstructure. The specific research objectives are: (1) to create a methodology to decouple and independently analyze the effects of heterovalency and lattice-mismatch at a contemporarily important model dissimilar semiconductor interface; (2) to thoroughly characterize the formation/nucleation, glide, and reaction dynamics of misfit dislocations at this interface; (3) to identify any fine structure at the interface resulting from the heterovalency; and (4) to determine the ultimate impact of heterovalency on the dislocation dynamics at this interface. This is accomplished by using a combination of novel sample design, epitaxial synthesis and a multi-scale suite of powerful structural characterization methods, emphasizing the holistic connection between heteroepitaxy, resultant interfacial morphology and strain-induced microstructure. The fundamental knowledge and scientific insight gained, and the novel methods developed within this effort, are directly applicable to nominally any dissimilar crystalline materials integration system.