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

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 In 0.8 Ga 0.2 Sb has a lower carrier concentration (~10 16 /cm 3 ), Te impurity was doped between low (1 × 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 In 0.8 Ga 0.2 Sb 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 × 10 18 /cm 3 . The carrier concentration in Te-doped In 0.8 Ga 0.2 Sb crystals were varied in the range 10 18 –10 20 /cm 3 . Te-doped In 0.8 Ga 0.2 Sb with concentration 1 × 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 In 0.8 Ga 0.2 Sb (1 × 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 In x Ga 1−x Sb is 1 x 10 18 /cm 3 for optimizing its properties toward mid-temperature thermoelectric applications.