Thermal conduction in AlxGa1−xN alloys and thin films

We report on experimental and theoretical investigation of thermal conduction in AlxGa1−xN alloys. A focus of this study is on understanding the effect of the Al mass fraction x and temperature on thermal conductivity in AlxGa1−xN thin films. The thermal conductivity of a set of AlxGa1−xN thin films as well as a pure GaN sample was measured using the differential 3ω technique in the temperature range from 80 to 400 K. Application of the virtual-crystal model allowed us to elucidate the strength of the mass-difference and strain-field-difference phonon scattering in AlxGa1−xN alloy system. The obtained thermal-conductivity temperature dependence indicates the high degree of disorder in the system. The measured variation of the thermal conductivity with the Al fraction x is in good agreement with the theory predictions. The measured data and calculation procedure are useful for evaluating the self-heating effect in AlxGa1−xN/GaN heterostructure field-effect transistors and for the device structure optimization.