Built-in-polarization field effect on lattice thermal conductivity of AlxGa1−xN/GaN heterostructure

• Built-in-polarization field enhances elastic constant, Debye temperature and their bowing constants in barrier material of AlxGa1−xN/GaN heterostructure.
• Thermal conductivity of AlxGa1−xN has been estimated and minimum value has been observed for x=0.5.
• Room temperature thermal conductivity of AlxGa1−xN/GaN heterostructure is enhanced by built-in-polarization field.
• The pyroelectric transition temperature of AlxGa1−xN alloy has been predicted for different x.

The built-in-polarization field at the interface of AlxGa1−xN/GaN heterostructure enhances elastic constant, phonon velocity, Debye temperature and their bowing constants of barrier material AlxGa1−xN. The combined phonon relaxation time of acoustics phonons has been computed for with and without built-in-polarization field at room temperature for different aluminum (Al) content (x). Our result shows that the built-in-polarization field suppresses the scattering mechanisms and enhances the combined relaxation time. The thermal conductivity of AlxGa1−xN has been estimated as a function of temperature for x=0, 0.1, 0.5 and 1 for with and without polarization field. Minimum thermal conductivity has been observed for x=0.1 and 0.5. Analysis shows that up to a certain temperature (different for different x) the polarization field acts as negative effect and reduces the thermal conductivity and after this temperature thermal conductivity is significantly contributed by polarization field. This signifies pyroelectric character of AlxGa1−xN. The pyroelectric transition temperature of AlxGa1−xN alloy has been predicted for different x. Our study reports that room temperature thermal conductivity of AlxGa1−xN/GaN heterostructure is enhanced by built-in-polarization field. The temperature dependence of thermal conductivity for x=0.1 and 0.5 are in line with prior experimental studies. The method we have developed can be used for the simulation of heat transport in nitride devices to minimize the self heating processes and in polarization engineering strategies to optimize the thermoelectric performance of AlxGa1−xN/GaN heterostructures.

The room temperature lattice thermal conductivity is enhanced by built-in-polarization field. For Al content, x=0.1, 0.5 and 1.0, the room temperature thermal conductivities for without (and with) built-in-polarization field are 185(204), 184(217) and 323(592) W m−1 K−1, respectively. Thermal conductivity measurement can reveal pyroelectric nature and can predict pyroelectric transition temperature. For x=0.1, 0.5 and 1.0, transition temperatures are close to 250, 230 and 100 K, respectively.Figure optionsDownload as PowerPoint slide