Bi-doped GaTe single crystals: Growth and thermoelectric properties

Abstract

Here bismuth (Bi) was utilized to substitute Te sites to increase the hole concentration, thereby enhancing the thermoelectric performance of GaTe. Bi-doped GaTe single crystals have successfully been fabricated by a temperature gradient technique. Bi atoms acting as acceptors helped to increase hole concentration from 9.43 × 1015 ​cm-3 for pristine GaTe to 0.63, 0.90, 1.20, and 1.63 × 1017 ​cm-3 for BGT-1, BGT-2, BGT-3, and BGT-4 single crystals, respectively. Moreover, the carrier mobility was increased up to 68.25 ​cm2 ​V-1 ​s-1 due to the crystallinity improvement of GaTe. Consequently, the electrical conductivity and power factor (PF) reached the respective maximum values of 3.62 ​S ​cm-1 and 1.21 ​μW ​cm-1 ​K-2 at 500 ​K for BGT-4 crystals. Meanwhile, Bi doping less affected the thermal transport properties of GaTe single crystals. A peak zT of ~0.02 was achieved at 700 ​K for the BGT-4 sample.