Abstract
The effect of low Al concentrations on the electronic structure and thermoelectric properties of Al(x)Ga(1-x)N/GaN (x = 0.1250, 0.1875, 0.2500, and 0.3125) heterojunctions was investigated using density functional theory and Boltzmann transport theory. Compared to Al(x)Ga(1-x)N/GaN heterojunctions with different Al concentrations, it was found that: (1) The bandgap increases and the density of states (DOS) decreases near the Fermi level as the Al concentration increases in Al(x)Ga(1-x)N/GaN heterojunctions. (2) The Seebeck coefficient of the Al(0.25)Ga(0.75)N/GaN heterojunction reaches 1850.20 μV/K at 300 K. (3) For n-type samples, the increase of Al concentration leads to higher conductivity in Al(x)Ga(1-x)N/GaN heterojunctions. (4) Power factor (PF) decreases with increasing Al concentration in Al(x)Ga(1-x)N/GaN heterojunctions. At the lowest Al concentration, the power factor of the Al(0.125)Ga(0.875)N/GaN heterojunction reaches 1.48 × 10(11)W/(m·K(2)·s) at 900K. (5) The maximum electronic thermoelectric quality factor (ZT(e)) of the Al(0.25)Ga(0.75)N/GaN heterojunction reaches 1.41, and at the same temperature, the n-type Al(x)Ga(1-x)N/GaN heterojunctions exhibit significantly higher performance than the p-type. The results are useful for exploring the thermoelectric properties of GaN-based heterojunctions and improving the performance of thermoelectric devices.