The thermal conductivities of β-Ga 2 O 3 single crystals along four different crystal directions were measured in the temperature range of 80-495K using the time domain thermoreflectance (TDTR) method. A large anisotropy was found. At room temperature, the [010] direction has the highest thermal conductivity of 27.0±2 .0 W/mK, while that along the [100] direction has the lowest value of 10.9±1.0 W/mK. At high temperatures, the thermal conductivity follows a ~1/T relationship characteristic of Umklapp phonon scattering, indicating phonon-dominated heat transport in the β-Ga 2 O 3 crystal. The measured experimental thermal conductivity is supported by first-principles calculations which suggest that the anisotropy in thermal conductivity is due to the differences of the speed of sound along different crystal directions.
Gallium nitride high-electron-mobility transistors (GaN HEMTs) are at a point of rapid growth in defense (radar, SATCOM) and commercial (5G and beyond) industries. This growth also comes at a point at which the standard GaN heterostructures remain unoptimized for maximum performance. For this reason, we propose the shift to the aluminum nitride (AlN) platform. AlN allows for smarter, highly-scaled heterostructure design that will improve the output power and thermal management of III-nitride amplifiers. Beyond improvements over the incumbent amplifier technology, AlN will allow for a level of integration previously unachievable with GaN electronics. State-of-the-art high-current p-channel FETs, mature filter technology, and advanced waveguides, all monolithically integrated with an AlN/GaN/AlN HEMT, is made possible with AlN. It is on this new AlN platform that nitride electronics may maximize their full high-power, high-speed potential for mm-wave communication and high-power logic applications.
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