Temperature and Stress Metrology of Ultra-Wide Bandgap β-Ga2O3 Thin Films

• Published in: 2018 17th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm) pp. 202 - 207
• Main Authors: Chatterjee, Bikramjit, Leach, Jacob H., Dhar, Sarit, Choi, Sukwon
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2018
• Subjects: Conferences; Gallium oxide; Raman scattering; stress measurement; temperature measurement; thermal stresses; wide band gap semiconductors
• ISSN: 2577-0799
• DOI: 10.1109/ITHERM.2018.8419526

The superior electronic properties of ultra-wide bandgap (UWBG) β-gallium oxide (β-Ga 2 O 3 ) gives promise to developing power and radio frequency (RF) devices with improved size, weight, and power (SWaP), and efficiency over current state-of-the-art wide bandgap (WBG) devices based on SiC and GaN. However, self-heating is viewed as a major challenge that the β-Ga 2 O 3 device technology will encounter. β-Ga 2 O 3 devices are expected to handle higher power densities than WBG counterparts. However, the thermal conductivity of β-Ga 2 O 3 is only on the order of 10-20 W/m-K, which is significantly lower than that for GaN or SiC. Therefore, large temperature gradients forming in β-Ga 2 O 3 devices during operation can cause thermo-mechanical reliability issues. In this work, a micro-Raman metrology scheme was established to simultaneously measure the temperature rise and associated thermo-elastic stress induced in β-Ga 2 O 3 thin films. To decouple the effect of temperature and stress, the proposed scheme utilizes multiple peaks in the β-Ga 2 O 3 Raman spectrum. A 1 μm thick halide vapor phase epitaxy (HVPE) β-Ga 2 O 3 layer grown on a sapphire substrate and a 3D thermo-mechanical multi-physics model was utilized to establish the measurement technique. The developed method can be used to determine the stress and temperature in β-Ga 2 O 3 epi-layers consisting future UWBG electronic devices.