Semiconductor Interface Electronics

This proposal covers basic research on heterojunction interfaces of semiconductors, such as GaN, having piezoelectric and spontaneous polarizations. The goal is to develop an understanding of fundamental effects in strained, pseudomorphic heterojunctions of this type, over a useful range of temperature. A set of twelve fundamental questions have been developed to direct the research. A team from Cornell University and Yale University has been assembled to cover the necessary research topics. Emphasis will be on GaN and related compounds and alloys. State-of-the-art MBE and OMVPE are available for these materials, along with an array of characterization equipment.

Means of optimizing the interactions of the team members has been planned. Fundamental theory of the electrical polarizations in the individual layers will be carried out, as well as the theory of screening by free carriers. The theory of phonon effects on carrier transport properties will be covered. Means of determining the properties of electric polarization uniformity will be established. Means of scaling these effects in alloys will be determined. High resolution optical probing, and high resolution STEM measurements will be undertaken to determine the uniformity of the polarization, and to compare it with the crystal structure.

Heterojunctions with only spontaneous polarization contributions, as well as those with piezoelectric polarizations, will be studied. Heterojunctions, barriers, and quantum wells with piezoelectric effects will be fabricated and characterized for carrier properties such as transport parallel and perpendicular to the interface, including improved Ohmic contacts, and recombination properties. Fundamental concepts of importance to improvement of future electron devices will be developed and modeled as a result of this research.

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