Study of Band Structure of Intermetallic Compounds by Pressure Experiments

The effect of hydrostatic pressure on the transport properties of n-type GaSb, InP, GaP, and p-type PbTe was measured to study their band structure. (1) The Seebeck coefficient, Hall coefficient, and resistance of three n-GaSb samples were measured as a function of hydrostatic pressure up to 17 000 atm between 200° and 400°K. The Seebeck coefficient α increased with pressure and approached a constant value at about 10 000 atm. The saturation value of α does not follow the simple 32 lnT relation for any of the samples; e.g., for a sample with RH(77°K) ≈95 coul−1 cm3, the saturation value of α decreases with temperature. The contribution due to the phonon-drag effect has been considered as a possible explanation for this phenomenon. (2) The conductivity of p-PbTe increased almost exponentially with pressure both at 300° and 194°K; the Hall coefficient at 300°K decreased by about 5% at 8000 atm, while the conductivity increased by 55% at this pressure. (3) The resistance of n-InP samples increased with pressure; the pressure coefficient was found to be bigger for samples with higher impurity contents. (4) The resistance of an n-GaP sample decreased by about 3% at 10 000 atm.