Anisotropic thermal conductivity of 4H and 6H silicon carbide measured using time-domain thermoreflectance

Silicon carbide (SiC) is a wide bandgap (WBG) semiconductor with promising applications in high-power and high-frequency electronics. Among its many useful properties, the high thermal conductivity is crucial. In this letter, the anisotropic thermal conductivity of three SiC samples, n-type 4H-SiC (N-doped 1 × 1019 cm−3), unintentionally doped (UID) semi-insulating (SI) 4H-SiC, and SI 6H-SiC (V-doped 1 × 1017 cm−3), is measured using femtosecond laser based time-domain thermoreflectance (TDTR) over a temperature range from 250 K to 450 K. We simultaneously measure the thermal conductivity parallel to (kr) and across the hexagonal plane (kz) for SiC by choosing the appropriate laser spot radius and the modulation frequency for the TDTR measurements. For both kr and kz, the following decreasing order of thermal conductivity value is observed: SI 4H-SiC > n-type 4H-SiC > SI 6H-SiC. This work serves as an important benchmark for understanding thermal transport in WBG semiconductors.