Thermoelectric Characteristics of Heavily Doped p-Type Lead Telluride at Different Heavy-Hole Band Depths

The full set of thermoelectric parameters of heavily doped p-PbTe in the temperature range of 300-1200 K at an acceptor doping level of N-a = 1 x 10(19)-4 x 10(20) cm(-3) and a heavy-hole band depth ranging from 0.36 to 0.7 eV is calculated. The figure-of-merit value Z is found to be highly sensitive to the doping level and increased by a factor of 1.5 with an increase in the dopant concentration from 1 x 10(19) to 5 x 10(19) cm(-3); the maximum Z value is found to correspond to N-a = (1-2) x 10(20) cm(-3). It is demonstrated that the change in the heavy-hole band depth leads to a noticeable shift of the Z maximum position along the temperature axis without noticeable Z maximum variation. The temperature corresponding to the maximum Z value is similar to that at which the top of the light-hole band crosses the Fermi level. The maximum calculateded ZT value is shown to be 1.64. At a heavy-hole band depth of 0.5 eV, the calculated results agree well with the available experimental data.