Non-monotonic thermoelectric behavior of lead telluride in quantum‐well‐like structures

Transport coefficients of quantum‐well‐like structures may in special circumstances show several interesting features. We have obtained theoretical expressions for transport coefficients including Lorenz factor and Seebeck coefficient in well-like structures taking into account the contributions from various sub-bands. Calculations based on the model have been presented for lead telluride quantum wells of varying well width (a). The results indicate a significant deviation in the transport behaviour as compared to the bulk particularly for a<100 nm. Unlike in the bulk material changes in Lorenz factors are rather less pronounced and at a=10 nm it is virtually a constant at 2.0. The Seebeck coefficient on the other hand shows a sharp rise below 100 nm. This region may be of particular interest in thermoelectric device applications. The results show an unusual behaviour of the Lorenz factor and Seebeck coefficient below a 100 nm well width. Moreover, contributions from quantized sub‐bands occupied up to the Fermi level may under certain conditions lead to a non-monotonic behavior which is also reported in some recent experimental measurements on particular PbTe quantum well structures.