Thermoelectric power of twohyphen;dimensional electron gas in heterojunctions at low temperatures

摘要

The lowhyphen;temperature thermopower of twohyphen;dimensional electron gas has been calculated by using the expression obtained from the Boltzmann equation. The relevant scattering mechanisms are taken into account. It is found that the calculated thermopower increases almost linearly with temperature in the GaAshyphen;AlGaAs and InGaAshyphen;InP structures, but in all cases the results differ widely from the values given by the Mott formula and also from the experimental values. The results are not influenced by phonon scattering and are slightly affected if the impurity density is changed by the order of magnitude. For highhyphen;mobility samples, the experimental values are higher than the theoretical ones and it seems that phonon drag thermopower may account for the difference. For lowhyphen;mobility samples, however, the experimental values are lower and in some cases decrease with temperature. The present model is then inadequate. Possible refinements of the theory are suggested.