Technical: This project explores the evolution of film stress, surface morphology and microstructure during the growth of InGaN by metalorganic chemical vapor deposition (MOCVD) on Ga-polar and N-polar GaN surfaces. A combination of in-situ wafer curvature measurements to probe dynamic changes in biaxial stress during MOCVD growth and post-growth transmission electron microscopy characterization will be emphasized. Initial studies will focus on investigation of compressive stress relaxation in InGaN grown on Ga-polar GaN on (0001) SiC substrates. The effects of N-rich vs group III-rich growth and intentional Si doping on stress relaxation, surface morphology and the structural and optical properties of the material will be studied early in the project. Comparable studies will then be carried out for N-polar InGaN/GaN grown on misoriented SiC. The project aims for identification and understanding of fundamental mechanisms of stress relaxation in InGaN, and the type and spatial distribution of resulting defects along with development of strategies to control stress and reduce defect formation.
The project addresses basic research issues in a topical area of materials science with technological relevance in electronics and photonics. The results from the proposed study are anticipated to yield new insights into the mechanisms of stress relaxation and microstructure evolution in Ga-polar and N-polar InGaN layers that can be exploited for improvements in photovoltaic and solid state lighting performance. The project forms the basis of Ph.D. thesis work of two graduate students; undergraduate students will also be involved in the research through REU programs at Penn State. The project enables the PI and her graduate students to collaborate with members of the Penn State MRSEC Center for Nanoscale Science and personnel at the Franklin Institute Museum in Philadelphia, PA on the development of a cart-based interactive demonstration kit on energy materials. The PI will assist in the development of module activities that utilize light emitting diodes to convey technical concepts such as light emission from semiconductor materials, color mixing and solid state lighting. The museum show on energy materials will initially be developed for visitors of the Franklin Institute but will also be distributed nationwide to at least twenty other science museums.
