Impurity diffusion in ion implanted AlN layers on sapphire substrates by thermal annealing

Funding Information: This work was supported by JSPS KAKENHI Grant No. 16H06424 and 19H02166, and the ARPA-E PNDIODES program. S. Suihkonen acknowledges the financial support of the Academy of Finland (grant 297916) and the Foundation for Aalto University Science and Technology. A part of the research was performed at the OtaNano—Micronova Nanofabrication Centre of Aalto University. This work was carried out through the use of MIT’s Microsystems Technology Laboratories, AIST NPF, and open facility in the University of Tsukuba. Publisher Copyright: © 2022 The Author(s). Published on behalf of The Japan Society of Applied Physics by IOP Publishing Ltd. We report on impurity diffusion in ion implanted AlN layers after thermal annealing. Silicon, tin, germanium, and magnesium ions were implanted into single-crystal Al-polar AlN layers grown on sapphire substrates. By annealing at 1600 °C, silicon and magnesium atoms were diffused in the AlN layer, while less change was observed in the distribution of germanium atoms. Silicon implantation introduced vacancy-related defects. By annealing at temperatures over 1300 °C, the vacancy-related defects were reduced, while oxygen atoms were diffused from the substrate due to sapphire decomposition. We reproducibly achieved silicon-implanted AlN layers with electrical conductance by controlling the annealing temperature and distribution of silicon and oxygen concentrations.