Measuring the thermal properties of wide bandgap semiconductors using an improved optical method based on high-modulation frequency laser

Wide bandgap semiconductors such as silicon carbide (SiC), aluminum nitride (AlN), and diamond are essential for high-power and high-frequency electronic devices due to their superior electrical and thermal properties. Accurate measurement of their thermal conductivity is critical for thermal management in advanced microelectronics. Traditional thermal measurement methods have a relatively low signal-to-noise ratio for materials with high thermal conductivity. In this work, we present an improved frequency-domain thermoreflectance (FDTR) method based on surface difference frequency generation, which involves the surface heterodyne of pump and probe lasers and significantly enhances the signal-to-noise ratio for measuring high-thermal-conductivity materials. The experimental setup was calibrated using sapphire and silicon dioxide standards, yielding thermal conductivity values consistent with the literature. We then measured the thermal properties of SiC, AlN, diamond, and nitrogen-doped diamond. The obtained thermal conductivities are 330.45 Wm⁻¹K⁻¹ for SiC, 248.5 Wm⁻¹K⁻¹ for AlN, 1202.78 Wm⁻¹K⁻¹ for diamond, and 302.87 W·m⁻¹·K⁻¹ for nitrogen-doped diamond. The results demonstrate the capability of the proposed method to accurately characterize materials with thermal conductivity ranging from 1 to over 1000 Wm⁻¹K⁻¹. This work provides a reliable and high-sensitivity approach for thermal property measurement of wide bandgap semiconductors.