Effects of Te-doping on the thermoelectric properties of InGaSb crystals

Abstract

Thermoelectric materials with optimum carrier concentration of the order of 10(19)-10(20)/cm(3) are required to obtain a high figure of merit (ZT) value. As undoped In0.8Ga0.2Sb has a lower carrier concentration (similar to 10(16)/cm(3)), Te impurity was doped between low (1 x 10(18)/cm(3)) and high level (1 x 10(21)/cm(3)) to understand the effects of doping on its thermoelectric properties. The undoped and Te-doped In0.8Ga0.2Sb crystals retained cubic zinc blende crystal structure irrespective of heavy doping of Te element. In addition to the optical phonon vibrational modes, acoustic phonon modes were also present when the doping concentration exceeded 1 x 10(18)/cm(3). The carrier concentration in Te-doped In0.8Ga0.2Sb crystals were varied in the range 10(18)-10(20)/cm(3). Te-doped In0.8Ga0.2Sb with concentration 1 x 10(18)/cm(3) was recorded a higher power factor because of its lower resistivity and higher mobility than other crystals. The ZT of Te-doped In0.8Ga0.2Sb (1 x 10(18)/cm(3)) was higher than other samples at 300-450 K. This study revealed that the optimum Te dopant concentration to enhance the ZT value of InxGa1-xSb is 1 x 10(18)/cm(3) for optimizing its properties toward mid-temperature thermoelectric applications.