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edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 21 NO. 2 14 drain. The temperature estimated directly from the GaN layer without the microparticles is averaged over the entire vertical structure and consequently is lower. These observations are independent of the power dissipation. All findings are in accordance with the literature. [6] CONCLUSION Raman spectroscopy has been shown to be useful for temperature measurement in GaN HEMTs. Micro-Raman thermography is able to achieve temperature and spatial resolution as high as ±5 C and 0.5–0.7 µm, respectively. A new technique was developed using cerium oxide mic- roparticles acting as micro-Raman thermometers. These particles permit temperature measurement of the semi- conductor surface aswell as themetal contacts, regardless of their roughness. This novel technique combines the benefits of thermoreflectance and classical Raman spec- troscopy, which permits probing of the semiconductor heterostructure from the surface to the substrate. REFERENCES 1. H. Amano, et al.: “The 2018 GaN Power Electronics Roadmap,” J. Phys. D: Appl. Phys., 2018, 51, p. 163001. 2. Y. Lv, X. Song, H. Guo, Y. Fang, and Z. Feng: “High-Frequency AlGaN/ GaN HFETs with f T /f max of 149/263 GHz for D-band PA Applications,” Electron. Lett., 2016, 52 (15), p. 1340-1342. 3. Y.C. Chou, et al.: “Degradation of AlGaN/GaN HEMTs under Eleva- ted Temperature Lifetesting,” Microelectron. Reliab., 2004, 44, p. 1033-1038. 4. Y.Q. Chen, et al.: “Degradation Mechanism of AlGaN/GaN HEMTs during High Temperature Operation Stress,” Semicond. Sci. Technol., 2018, 33, p. 015019. 5. J. Brown, P.K. Footner, and B.P. Richards: “Failure Analysis of Plastic Encapsulated Components - the Advantages of IR Microscopy,” J. Microsc., 1987, 128 (2), p. 179-194. 6. M. Kuball and J.W. Pomeroy: “A Review of Raman Thermography for Electronic andOpto-ElectronicDeviceMeasurementwithSubmicron Spatial andNanosecond Temporal Resolution,” IEEE Trans. Dev. Mat. Reliab., 2016, 16 (4), p. 667-684. 7. P.M. Mayer, D. Lüerben, and J.A. Hudgings: “Theoretical and Experimental Investigation of the Resolution and Dynamic Range of CCD-Based Thermoreflectance,” J. Opt. Soc. Am. A., 2007, 24 (4), pp. 1156-1163. 8. S. Choi, E.R. Heller, D. Dorsey, R. Vetury, and S. Graham: “Thermom- etry of AlGaN/GaN HEMTs using Multispectral Raman Features,” IEEE Trans. Electron Dev., 2013, 60 (6), pp. 1898-1904. 9. M. Farzaneh, et al.: “CCD-Based Thermoreflectance Microscopy: Principles and Applications,” J. Phys. D: Appl. Phys., 2009, 42 (14), p. 143001. 10. C. Yuan, J.W. Pomeroy, and M. Kuball: “Above Bandgap Thermo- reflectance for Non-Invasive Thermal Characterization of GaN-Based Wafers,” Appl. Phys. Lett., 2018, 113 (10), p. 102101. 11. C.V. Raman and K.S. Krishnan: “ANewType of Secondary Radiation,” Nature, 1928, p. 501. 12. T. Beechem, S. Graham, S.P. Kearney, L.M. Phinney, and J.R. Serrano: “Simultaneous Mapping of Temperature and Stress in Microdevices using Micro-Raman Spectroscopy,” Rev. Sci. Instr., 2007, 78 (6), p. 61301. 13. J.B.Cui,K.Amtmann,J.Ristein,andL.Ley:“NoncontactTemperature Measurements of Diamond by Raman Scattering Spectroscopy,” J. Appl. Phys., 1998, 83 (12), pp. 7929-7933. 14. R.J.T. Simms, J.W. Pomeroy, M.J. Uren, T. Martin, and M. Kuball: “Channel Temperature Determination in High-Power AlGaN/ GaN HFETs using Electrical Methods and Raman Spectroscopy,” IEEE Trans. Electron Dev., 2008, 55 (2), p. 478-482. 15. J.W. Pomeroy andM. Kuball: “Solid Immersion Lenses for Enhancing theOptical Resolutionof Thermal andElectroluminescenceMapping of GaN-on-SiC Transistors,” J. Appl. Phys., 2015, 118 (14), p. 144501. 16. F. Berthet, Y. Guhel, H. Gualous, B. Boudart, J.L. Trolet, M. Piccione, and C. Gaquière: “Characterization of the Self-Heating of AlGaN/GaN HEMTs during an Electrical Stress by using Raman Spectroscopy,” Microelectron. Reliab., 2011, 51 (9–11), p. 1796-1800. 17. G.J. Riedel, et al.: “Nanosecond Timescale Thermal Dynamics of AlGaN/GaN Electronic Devices,” IEEE Electron Device Lett., 2008, 29 (5), p. 416-418. 18. O. Lancry, E. Pichonat, J. Réhault, M. Moreau, R. Aubry, and C. Gaquière: “Development of Time-Resolved UV Micro-Raman Spectroscopy to Measure Temperature in AlGaN/GaN HEMTs,” Solid-State Electron., 2010, 54 (11), p. 1434-1437. ABOUT THE AUTHORS Bertrand Boudart received his M.S. and Ph.D. degrees in electronic engineering and solid-state physics from Louis Pasteur University, Strasbourg, France, in 1988 and 1992, respectively. In 1992, he joined the Institut d’Electronique et de Microélectronique du Nord (IEMN), Lille, France, where he worked on power HEMTs for millimeter-wave amplification. His investigations included GaAs, InP, and GaN-based devices. He has been a professor at the University of Caen, France, since 2001 and conducts research at the Groupe de Recherche en Informatique, Image, Automatique & Intrumentation de Caen (GREYC). He is primarily involved in GaN and Raman spectroscopy activities. Yannick Guhel received a Ph.D. in electronics from the IEMN, Lille, France, in 2002. He then joined theUniversity of Caen and conducts research at the GREYC. His research activities include the techno- logical process of devices, depositionof thin films by sputtering, impact of electrical stress and gamma and neutron irradiation on the electrical behavior of GaN-based devices, and Raman spectroscopy.