Unexpected Enhanced Thermal Conductivity of GaXIn1-XSb Ternary Alloys

Alloying is one of the most common approaches to modulate the properties of semiconductors, such as indium antimonide (InSb) with practical applications in mid-infrared optoelectronics. Thermal conductivity plays a key role in governing the operating performance of devices, and the high-efficiency regulation is of great significance to desirable applications. In this study, we studied the thermal transport properties of InSb, GaSb, and their GaxIn1-xSb alloys by solving the Boltzmann transport equation based on first-principles calculations. The thermal conductivity of GaxIn1-xSb alloys (x = 0.25, kappa = 9.21 Wm-1 K-1; x = 0.5, kappa = 11.22 Wm-1 K-1; and x = 0.75, kappa = 15.45 Wm-1 K-1) is enhanced compared with that of InSb (kappa = 5.15 Wm-1 K-1), which is unlike the conventional belief that alloying usually reduces thermal conductivity. Through fundamental analysis of phonon transport properties, the higher phonon group velocity and phonon relaxation time caused by the weak phonon anharmonicity lead to higher thermal conductivity of the GaxIn1-xSb alloys. The weakened polarization of GaxIn1-xSb alloys occurring in the alloying process generates the increased thermal conductivity, which can be figured out by analyzing the orbital-projected electronic density of states and the electron localization functions. The underlying mechanism of unconventional high thermal conductivity of the GaxIn1-xSb alloys in this study would provide guidance for the device applications accompanied by thermal transport.