Epitaxial AlN Thin Film Surface Acoustic Wave Devices Prepared on GaN/Sapphire Using Low-Temperature Helicon Sputtering System

Abstract

High-quality epitaxial AlN films have been deposited on GaN/sapphire using helicon sputtering at a temperature of 300 C. The surface acoustic wave (SAW) characteristics, in terms of insertion loss, stopband rejection, and electromechanical coupling coefficient, of SAW devices fabricated on AlN/GaN/sapphire are much superior than those fabricated on GaN/ sapphire. The investigation of environmental effects, including temperature and relative humidity, shows that the ambient stability can be improved with the deposition of an AlN film on GaN/sapphire. An oscillator fabricated using an AlN/GaN/ sapphire-based SAW device was developed for application in sensors. The composite structure of AlN on GaN may bring about the development of high-frequency components, which integrate and utilize their semiconducting, optoelectronic, and piezoelectric properties.

Carbothermal Reduction Synthesis of Aluminum Nitride from Al(OH)3/C/PVB Slurries Prepared by Three-Roll Mixing

“…In the past twenty years, increasing attention has been paid to aluminum nitride (AlN) including AlN thin films, ceramics and composites due to high thermal conductivity, high electrical resistivity, good electrical insulation, non-toxicity and thermal expansion coefficient close to that of silicon [ 1 , 2 ]. AlN thin films with high band gap (~6.2 eV), acoustic velocity and a substantial electromechanical coupling coefficient were used for surface acoustic wave (SAW), bulk acoustic wave (BAW) and heterojunction diodes devices in piezoelectric and semiconducting fields [ 3 , 4 , 5 ]. Using AlN powder as raw material, AlN ceramics with high thermal conductivity (>170 W/(m⋅K)), low dielectric constant (~8.8) and loss (~10 −4 ) could be prepared by tape casting and sintering, which were usually used for substrate material of large-scale integrated circuit and high-power packaging of light-emitting diodes (LED) in electronic and optoelectronic fields [ 1 , 6 ].…”

Fabrication of Low-Residual-Stress AlN Thin Films and Their Application to Microgenerators for Vibration Energy Harvesting

“…As for AlN thin films, which have been widely used as piezoelectric material, [5][6][7] the optimization of the ECR deposition parameters such as sputtering pressure, power, and gas flow rate have been reported to partially reduce the residual stress. 8,9) In this study, one research objective of ours is to adopt another method of selecting different bottom electrodes to further reduce the residual stress of AlN thin films.…”