High thermoelectric power factors in polycrystalline germanium thin films

The high potential of polycrystalline Ge as a thin-film thermoelectric material was demonstrated. We synthesize a polycrystalline Ge layer on an insulating substrate at 450 & DEG;C via advanced solid-phase crystallization and control its carrier concentration through the solid-phase diffusion of various p- and n-type dopants. The heating deposition (150 & DEG;C) of the amorphous precursor considerably improves the crystal quality of the polycrystalline Ge layer as well as the doping properties. The solid-phase diffusion of Ga and P dopants onto the Ge layers allows for control of the carrier concentration in the ranges of 10(17)-10(20) cm(-3) for p-type and 10(18)-10(19) cm(-3) for n-type, respectively, by modulating the diffusion annealing temperature and time. Because of the high electrical conductivities reflecting the carrier mobilities and carrier concentrations, the maximum power factors reach a value of 1080 mu W m(-1) K-2 for p-type and 2300 mu W m(-1) K-2 for n-type at room temperature. These power factors are higher than those of most polycrystalline semiconductor thin films formed at temperatures below 1000 & DEG;C. Therefore, this study serves as a milestone toward high-performance and reliable thin-film thermoelectric generators based on an environmentally friendly semiconductor.

Automated summary

A high potential for polycrystalline Ge as a thin-film thermoelectric material has been demonstrated, with carrier concentration controlled through solid-phase diffusion of various dopants. Improved crystal quality and doping properties were achieved through advanced solid-phase crystallization and heating deposition techniques. The achieved power factors surpass those of most polycrystalline semiconductor thin films formed at lower temperatures, marking a milestone towards high-performance thin-film thermoelectric generators based on environmentally friendly semiconductors.