Temperature induced electrical transport in n-Bi₂Te₃/p-InAs thermoelectric heterojunctions

Thermoelectric semiconductor devices have recently attracted more interest since their electrical properties can be further adjusted by the temperature field. Many efforts have been made in thermoelectric junctions based on bismuth telluride (Bi₂Te₃) when the temperature gradient is parallel to the direction of the built-in field. However, the influence of thermoelectric effect on electrical transport behavior with temperature gradient in other directions is rarely reported. Here, we fabricated the n-Bi₂Te₃/p-InAs thermoelectric heterojunctions by the modified hot wall epitaxy (HWE) method, and mainly studied the band alignment of the heterojunction and the dependence of the current–voltage (I–V) characteristics on temperature gradient in different directions. The forward current was obviously enhanced and a unique reverse current peak was also observed when the temperature gradient was perpendicular to built-in field (lateral direction), owing to the thermoelectricity induced wedge-shaped depletion region, which resulted in the carrier diffusion on the cold side at forward bias and minority carrier drift boost on the hot side at reverse bias. The obtained results provide a new way to fabricate a diode device with temperature difference switch, and the self-powered photodetector.