Electrical properties of the high-pressure phases of gallium and indium tellurides

A study has been made of the resistance ρ, the thermopower S, and magnetoresistance MR of Ga2Te3 and α-In2Te3 single crystals at pressures P up to 25 GPa. It is found that the resistance ρ and |S| sharply decrease at ∼0–5 and 1.5–3 GPa, respectively. The semiconductor-metal phase transitions in the temperature range from 77 to 300 K are established from the sign reversal of the temperature coefficient of ρ to occur at P>4.4 and >1.9 GPa. The values S ≈+(10–20)µ V/K for the metallic phases with a Bi2Te3-type structure agree with those for liquid In2Te3 and Ga2Te3. Negative MR is revealed in In2Te3 at P≈1.9 GPa. No MR is observed in Ga2Te3 up to 25 GPa. The variation of the electronic structure of In2Te3 and Ga2Te3 under pressure is discussed.