Experimental observation of high intrinsic thermal conductivity of AlN

Wurtzite AlN is an ultrawide bandgap semiconductor that has been developed for applications including power electronics and optoelectronics. Thermal management of these applications is the key for stable device performance and allowing for long lifetimes. However, the intrinsic high thermal conductivity of bulk AlN predicted by theoretical calculations has not been experimentally observed because of the difficulty in producing high-quality materials. This work reports the growth of thick (>15 μm) AlN layers by metal-organic chemical vapor deposition and experimental observation of intrinsic thermal conductivity from 130 to 480 K that matches density-functional-theory calculations for single crystal AlN, producing some of the highest values ever measured. Detailed material characterizations confirm the high quality of these AlN samples with one or two orders of magnitude lower impurity concentrations than commercially available bulk AlN. The thermal conductivity of these commercially available bulk AlN substrates are also measured as comparison. To interpret the reduced thermal conductivity, a simple Callaway model is built. This work demonstrates the possibility of obtaining theoretically high values of thermal conductivity in AlN and will impact the thermal management and reliability of future electronic and optoelectronics devices.