(Invited) Defects and Development of High Power Vertical GaN Based Structures

Abstract

This presentation highlights the use of x-ray scattering and electron microscopy to characterize selectively doped GaN layers for high power vertical diodes. Examples from these techniques will include assessment of residual impurities and crystalline damage in selectively doped regions resulting from dry etching or ion implantation processes and if such defects are removed by subsequent etching and / or annealing steps. X-ray reflectivity (XRR) combined with high angle reciprocal space mapping and dynamical diffraction simulations are effective means by which to assess the strain and defect distribution in the wafers. Advanced synchrotron techniques, through the use of hard x-ray nanoprobes and diffraction imaging, offer further insight into the development of these technologies. Transmission Electron Microscopy measurements, including electron energy loss spectroscopy, energy dispersive x-ray analysis, and selected area diffraction patterns, determine whether impurities were introduced by the selective doping process and whether the damage removal processes were able to remove growth and implantation-induced defects. A better understanding of the roles of defects on device performance is based on these techniques.