期刊
ACTA MATERIALIA
卷 203, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.116495
关键词
Ion implantation; Piezoelectricity; Defect; III-N Semiconductor; Polarisation
资金
- New Zealand Ministry for Business, Innovation and Employment [C05 x 1712]
- Australian Research Council (ARC) - Linkage, Infrastructure, Equipment and Facilities (LIEF) grants [LE120100104, LE160100063]
- Advanced Light Source, a U.S. DOE Office of Science User Facility [DE-AC02-05CH11231]
The evolution of uniaxial strain in Zr+ implanted epitaxial AlN films on Si substrates leads to an expansion of the c-axis in the crystal structure, with the main defects being Zr-Al, V-Al, and V-N. Monte Carlo simulations predict the formation of cation-rich and anion-rich regions within the implantation range, with an anion-rich layer undergoing a polarity inversion. The effective piezoelectric coefficient decreases as the fluence of Zr+ increases, due to strain- and compositionally-induced polarity changes and crystalline damage.
We report the evolution of uniaxial strain, resulting in an expansion of the c-axis in the wurtzite structure by up to 1 %, without significant degradation of the crystal structure of 30 keV Zr+ implanted epitaxial AlN films, grown on Si substrates. Raman and X-ray absorption spectroscopies demonstrated that the dominant defects are Zr-Al, V-Al and V-N. The uniaxial strain can be attributed to a weakening of the Metal-N pi bond along the c-axis. Monte Carlo simulations further predict the formation of a cation-rich region within the Zr implantation range, along with a buried anion-rich layer for all investigated fluences. The anion-rich layer undergoes a polarity inversion, which was experimentally confirmed by high-resolution high-angle annular dark field scanning transmission electron microscopy. Those microstructural changes influence the macroscopic electromechanical properties of AlN. The effective piezoelectric coefficient, d(33), reduces from (7.0 +/- 0.5) pm/V to (5.2 +/- 0.5) pm/V at a fluence of 10(15) at./cm(2) Zr+. At higher fluences AlN undergoes a strain- and compositionally-induced polarity change, and the piezoelectric coefficient decreases due to crystalline damage. These results provide a pathway to optimise the performance of AlN by ion implantation for applications such as energy harvesting, light-emitting diodes and acoustic wave devices. In addition, the capability to engineer a buried polarisation inversion after AlN growth may enable novel device design. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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