Optimizing the thermoelectric performance of InGaZnO thin films depending on crystallinity via hydrogen incorporation

Abstract

The thermoelectric power factor of amorphous (a-IGZO), c-axis aligned crystalline (c-IGZO) and (cc-IGZO) crystal-embedded c-axis aligned crystalline InGaZnO were optimized by performing hydrogen incorporation via post-annealing. Highest power factor was achieved for a-IGZO when annealing with pure N2 was used, while adding 4% H2 in the N2 atmosphere significantly enhanced those of c-IGZO and cc-IGZO. However, the cc-IGZO samples displayed weaker properties compared to both a-IGZO and c-IGZO regardless of the annealing conditions. The presence of H2 was effective in passivating oxygen-related defects for both the c-IGZO and cc-IGZO samples, which translated to better electron transport while maintaining a respectable Seebeck coefficient. On the other hand, the formation of a high amount of oxygen vacancies from annealing with pure N2 was likely responsible not only for the good electrical conductivity of a-IGZO, but also for the relatively good Seebeck coefficients. Establishing the post-annealing conditions to maximize the thermoelectric properties depending on crystallinity paves the way for future commercial transparent IGZO thermoelectric devices.