Cu-induced Seebeck peak in HMS/Si film

Abstract

It is well known that aluminum ( Al ), boron ( B ) and copper ( Cu ) are acceptor impurities with shallow- and deep-energy levels in silicon ( Si ), respectively. Thus, Al and B impurities with shallow-energy levels in Si are essentially completely ionized at room temperature while Cu impurities with deep-energy levels in Si at higher temperature. In this paper, Al , B and Cu co-doped Si layer is used as a barrier layer while the higher manganese silicide layer (HMS) as a well layer. The Seebeck coefficient (S) of Al and Cu modulation doped film, HMS/ Si :( Al + Cu ), increases sharply above 583 K, reaches a peak value of 0.300 mV/K at 683 K, and then decreases with further increasing temperature. Concomitance with the great increase in Seebeck coefficient, however, the electrical resistivity (R) is still smaller than that of only Al modulation doped film, HMS/ Si : Al . The Cu -induced Seebeck peak, S max = 0.303 mV/K at 733 K, and reduction in electrical resistivity are also observed in ( B + Al + Cu ) modulation doped film, Si :( B + Al + Cu )/HMS/ Si :( B + Al + Cu ), where B is used to reduce the electrical resistivity further. As a result, the thermoelectric power factor (PF = S2/R) is greatly enhanced and can reach 3.140 × 10-3 W/m-K2 at 733 K, which is larger than that of HMS bulk material.