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

Highlights

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First systematic measurement of the anisotropic thermal conductivity of 4H and 6H SiC.

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The thermal conductivity of SiC samples are observed to be: k(SI 4H) > k(n-type 4H)> k(SI 6H).

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Important benchmark for understanding thermal transport in WBG semiconductors.

Abstract

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 $\left(k_r\right)$and across the hexagonal plane $\left(k_z\right)$ for SiC by choosing the appropriate laser spot radius and the modulation frequency for the TDTR measurements. For both $k_r$ and $k_z$, 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.

Source:ScienceDirect

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