Thermoelectric effect in suspended Bi₂Se₃ grown by molecular beam epitaxy on GaAs(111)A

Bi₂Se₃ is well known as an efficient thermoelectric (TE) material. We report growth optimization of Bi₂Se₃ thin films and thermoelectric study of suspended Bi₂Se₃ beam structures. The Bi₂Se₃ thin films were grown on GaAs(111)A substrates by molecular beam epitaxy (MBE) and confirmed by (00n) series peaks of x-ray diffraction (XRD) that the material was grown along the c-axis of GaAs(111)A. Optimizing the desorption process of GaAs(111)A surface and growth conditions of GaAs buffer layers leads to low RMS roughness and less-defective structural aspect. Using the optimizied Bi₂Se₃ films, we realize the suspended beam structures with minimal heat dissipation to GaAs substrate. The beam structures are fabricated by selective wet etching, and on the two membranes, platinum heaters and voltage channels are patterned to measure the thermoelectric effect, the conversion of temperature difference to electric voltage. Nanomachining technique enables to calculate the dimensionless figure of merit (ZT) of Bi₂Se₃ with minimal environmental factors.