ICT2014 Abstracts

Band engineering in semiconductors is important for their application in electronic or optoelectronic devices. For heavily doped thermoelectric semiconductors it is also crucial for the high zT found in PbTe1-xSex, Pb1-xMgxTe, and Mg2Si1-xSnx. For high temperature bulk thermoelectrics, most of such engineering is realized by forming solid solutions. In this study we demonstrate successful band tuning of p-type PbSe, the slightly lower zT analog of the well-known ther- moelectric compound PbTe, using Pb1␣xSrxSe solid solutions. It is well known that formation of solid solutions is desirable for thermoelectrics due to their lower thermal conductivities. We demonstrate here that the ability to change not only the band gap but also the relative positions of different band maxima provides another important benet for solid solutions as thermoelectrics. Actually, we found in these alloys that the reduction of lattice thermal conductivity by alloying has been compensated by the counter effect of the reduced carrier mobility, as also been found in the n-type solid solutions PbTe1␣xSex and PbSe1␣xSx where simply forming solid solutions without the band engineering effect does not improve zT. Therefore we conclude that the change in the band structure with formation of solid solution accounts for the improvement of zT in p-type PbSe from 1.1 to 1.5 at 900 K.