【Member Papers】Electro-thermal crosstalk revealed by Raman thermography in multi-fin β-Ga₂O₃ FinFETs

      Researchers from the Xi’an Jiaotong University and Xidian University have published a dissertation titled " Electro-thermal crosstalk revealed by Raman thermography in multi-fin β-Ga₂O₃ FinFETs" in Applied Physics Letters.

Background

      β-Ga₂O₃ has emerged as a highly promising material for next generation high-power electronic applications owing to its superior intrinsic properties. These include a wide direct bandgap of 4.8 eV (Eg), an exceptionally high critical electric field of 8 MV/cm, a moderate carrier mobility of 250−300 cm²/Vs , a high electron saturation velocity of 1.8−2×10⁷ cm/s , and a high theoretical Baliga’s figure of merit (BFOM). While absolute values vary depending on critical electric field estimates,3 it is widely projected to be approximately 3444 times that of Si. Furthermore, the growth technology of β-Ga₂O₃ is relatively well developed, allowing for controllable n-type doping across a wide concentration range (10¹⁶-10¹⁹ cm^-3). The availability of high-quality, low-cost bulk substrates produced via melt growth methods also provides unique opportunities for the fabrication of cost-effective, high-performance transistors. This advantage directly addresses the high manufacturing costs associated with SiC and GaN, thereby paving the way for the advancement of device technologies 8–10 and their potential large-scale commercialization.

Abstract

      β-Ga₂O₃ FinFETs are promising for high-power electronic applications owing to their ultra-wide bandgap and high breakdown field. To overcome the inherently limited current capability of single-fin devices, multi-fin architectures were introduced to enhance the total on-state current. However, transfer characteristics reveal that when the fin number is increased by a factor of 16, the saturation current at V_D =10 V rises only from 0.112 to 1.22 mA—significantly below the expected linear scaling—and premature current degradation emerges at high V_G Such deviation indicates pronounced self-heating and electro-thermal coupling within densely packed fin arrays. Furthermore, under high power operation, evident nonlinearities appear in both temperature rise and current response, further supporting the thermally driven origin of performance degradation. Raman thermography under identical per-fin current conditions reveals a much higher peak temperature (70.77 °C) in the multi-fin device compared to the single-fin counterpart (28.8 °C), confirming severe thermal crosstalk. These findings elucidate the thermal origin of the non-ideal current scalability and provide essential insights for thermally aware three-dimensional design of β-Ga₂O₃ FinFETs.

Highlights

      Combining submicron-resolution Raman thermography with electrical measurements, the study achieves accurate spatial temperature characterization of β-Ga₂O₃ multi-fin/single-fin FinFETs under the condition of equal power per fin, and also calibrates and selects a highly sensitive Raman temperature measurement mode while considering the influence of stress on temperature measurement, thus improving the accuracy of thermal characterization.

      An electro-thermal compact model adapted to β-Ga₂O₃ is constructed, the current scaling efficiency φ(N) is defined for the first time and the effective mobility-temperature exponent m_eff≈14 is extracted, realizing the quantitative evaluation of thermally induced current degradation and non-ideal current scaling of such devices.

      The study systematically reveals that thermal crosstalk caused by the low and anisotropic thermal conductivity and the geometric constraints of high-density fin arrays is the core thermal cause of non-ideal current scaling in β-Ga₂O₃ multi-fin FinFETs, and proposes the device design optimization directions of moderately reducing the number of fins and optimizing the three-dimensional layout.

Conclusion

      In this work, we investigated the electro-thermal behavior of β-Ga₂O₃ slanted FinFETs using combined electrical characterization and three-dimensional Raman thermography. Although the multi-fin configuration increases the total on-state current compared with a single fin, the gain is far below proportional scaling and is accompanied by premature current saturation. Raman mapping under identical per-fin power reveals a peak temperature of 70.77 °C for the 16-fin array vs 28.8 °C for the single-fin device, indicating strong thermal coupling and inefficient heat spreading in densely packed fins. Together with an electro-thermal compact model, these results yield a large mobility– temperature exponent ( m≈14 ) and a reduced current-scaling efficiency [φ(16)≈0.68] , demonstrating that self-heating and thermal crosstalk fundamentally constrain current scalability and that moderating fin number and optimizing three-dimensional layouts will be crucial for future high-power β-Ga₂O₃ devices.

Project Support

      This work was supported by the National Natural Science Foundation of China under Grant Nos. 62474133, 62374174, and U2241220, the Guangdong Basic and Applied Basic Research Foundation under Grant No. 2025A1515011176, and the fundamental research funds for the central universities of China under Grant No. QTZX23019.