(Invited) Effect of Seed Crystal Orientation on Ammonothermal Growth of GaN

Abstract

Gallium nitride (GaN) is a wide bandgap semiconductor which has received widespread attention as it has enabled the development of short wavelength (UV, blue) optical emitters and promises a new generation of high efficiency power electronic devices. To enable widespread use of high power, high efficiency devices, the availability of large-area, inexpensive, low-defect-density GaN substrates is necessary.The ammonothermal method is a bulk, single crystal growth method which has demonstrated growth of high structural quality GaN boules greater than 2 inches in diameter. Despite these demonstrations, challenges remain with regards to improving growth rates to reduce cost of boules and understanding the growth behavior of GaN in these environments to further improve upon crystal quality. In particular, the general trend and affect of the GaN seed crystal on growth rates and crystal quality has not been studied in detail.This talk will discuss our current understanding of how the initial seed crystal orientation affects the resulting ammonothermal GaN growth, surface morphology, crystal quality, and impurity incorporation. Seed crystals were sourced from hydride vapor phase epitaxial (HVPE) grown GaN boules that were sliced and polished to atomically smooth crystallographic facets of varying orientations. Three series were created resulting in incrementally changing orientations ranging from +c-plane to m-plane to -c-plane, from +c-plane to a-plane to -c-plane and from m-plane to a-plane.