Study of the thermal properties of wurtzite AlN crystals based on different facets

Abstract

Aluminum nitride (AlN) crystals, as a typical representative of wide bandgap semiconductor materials, are being widely used in high-performance power electronics and optoelectronics devices. However, the high-power density of the devices poses new challenges for thermal management, therefore, there is an urgent need to enhance the study of thermal properties of AlN crystals, especially for crystals with different orientations. In this work, (0001) and (10−11) oriented AlN crystals are taken as examples for comparative study. Thermal conductivity is measured from room temperature to 300 °C using a laser flash method. The data within the tested temperature range are fitted, revealing the functional forms of thermal diffusivity and thermal conductivity as a function of temperature. It is found that thermal conductivity is proportional to T⁻ⁿ, where 1 < n < 2, consistent with observations in 4H-SiC and 6H-SiC. The temperature dependent thermal properties are evaluated in both orientations revealing weak anisotropy in thermal conductivity. In addition, various factors affecting the thermal properties of AlN crystals are discussed. These findings provide valuable insights for the development of AlN-based devices.