Investigation of Temperature Sensing Capabilities of GaN/SiC and GaN/Sapphire Surface Acoustic Wave Devices

• Published in: IEEE access Vol. 10; pp. 741 - 752
• Main Authors: Boldeiu, George, Ponchak, George E., Nicoloiu, Alexandra, Nastase, Claudia, Zdru, Ioana, Dinescu, Adrian, Muller, Alexandru
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic resonance; Carrier density; Finite element method; Gallium nitrides; GaN; High temperature; high temperature measurements; Low temperature; low temperature measurements; Mathematical models; Polynomials; Resonant frequency; Room temperature; Sapphire; SiC; Silicon carbide; Silicon substrates; Substrates; Surface acoustic wave; Surface acoustic wave devices; Surface acoustic waves; Temperature; Temperature measurement; temperature sensor; Temperature sensors
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2021.3137908

This paper proposes high sensitivity temperature sensors based on single port surface acoustic wave (SAW) devices with GHz resonance frequencies, developed on GaN/SiC and GaN/Sapphire, which permit wide range, accurate temperature determinations. In contrast with GaN/Si SAW based temperature sensors, SiC and Sapphire substrates enable the proper functionality of these devices up to 500°C (773 K), as the high resistivity Si substrate becomes conductive at temperatures exceeding 250°C (523 K) due to the relative low bandgap (and high intrinsic carrier concentrations). Low temperature measurements were carried out using a cryostat between -266°C (7 K) and room temperature (RT) while the high temperature measurements are made on a modified RF probe station. A polynomial fit was used below RT and a linear approximation was evidenced between RT and 500°C (773 K). The structures were simulated at different selected temperatures based on a method that couples Finite Element Method (FEM) and Coupling of Modes (COM). The measured temperature coefficient of frequency (TCF) is about 46 ppm/°C for GaN/SiC SAWs and reaches values of 96 ppm/°C for GaN/Sapphire SAW in the temperature range 25 - 500°C (298 K - 773 K).