Enhancement of thermoelectric power factor by a silicon spacer in modulation-doped Si-HMS-Si

The introduction of an un-doped silicon layer (spacer) enhances significantly the thermoelectric power factor in modulation-doped Si(Al)-MnSi(1.7)-Si(Al) sandwich structure. This un-doped silicon layer is inserted between the MnSi(1.7) (HMS) and Al-doped silicon layers. With a proper spacer thickness, the electrical resistivity decreases sharply and is weakly dependent on temperature from 300K to 683 K. As a result, the thermoelectric power factor can reach 0.973 x 10(-3) W/m-K(2) at 683 K, which is about ten times larger than that of an ordinary MnSi(1.7) film without modulation doping.