Ousmane I Barry
Nagoya University, Japan
Title: Growth and characterization of homoepitaxial m-plane GaN on native bulk GaN substrates: Prospects of next-generation electronic devices
Biography
Biography: Ousmane I Barry
Abstract
Nonpolar (m–plane) nitride heterostructures-based electronic devices are, unlike their polar (c-plane) counterparts, devoid of spontaneous polarization and piezoelectric fi elds. Th is unique feature makes nonpolar nitride materials very promising candidates for normally-off enhancement mode transistors which are highly demanded in safe power switching operation and also for very stable light emitters owing to the suppression of the quantum confi ned Stark eff ect. Recent breakthroughs in the bulk GaN growth technology have made low defect m–plane GaN substrates commercially available, paving the way for higher-quality homoepitaxial GaN growth and the development of vertical devices. However, the growth of nominally on-axis homoepitaxial GaN layers by metal-organic vapor phase epitaxy (MOVPE) on these native substrates generates wavy surface reliefs characterized by three-dimensional four-sided pyramidal hillocks which are detrimental for device fabrication. In addition, a higher unintentional impurity incorporation in non-polar nitride fi lms hinders device performance and reliability. In this talk, we present a technique to reduce the formation of pyramidal hillocks on the homoepitaxial m-GaN fi lms. Smooth surfaces with very low density of hillocks are achieved under high V/III ratio and exclusively N2 carrier gas. Th e electrical properties of m-GaN fi lms were found to be dependent on the surface morphology. A clear improvement of the electrical properties can be observed by suppressing the hillocks. Subsequently, impurities concentrations in m-GaN fi lms were signifi cantly reduced with V/III optimization and pure N2 carrier gas as confi rmed by SIMS analysis. Th ese results show good prospects for the development of next-generation electronic devices on non-polar GaN materials.