Piezo-thermoelectromotive force in strained p-GaAs samples

Abstract

Experimental data are given on the thermo-emf in strained samples of p-type gallium arsenide with hole densities of 10¹⁷ to 10¹⁹ cm⁻³ in the temperature range from 77 to 400°K. It is shown that the thermo-emf in the strained samples depends on the degree of doping and orientation of the original crystals. Phonon drag is observed in strained p-GaAs samples at a temperature of about 100°K. A maximum of the dependence α=f(T) is observed in the <111> direction, and a minimum of the thermo-emf in the <100> direction. The indicated behavior of the thermo-emf can be explained by anisotropy of the hole effective masses. It is postulated that scattering of holes by acoustic lattice vibrations and by impurity ions takes place in the case of p-GaAs samples with a hole concentration of 10¹⁷ cm⁻³, whereas only scattering by impurity ions takes place for samples with p=10¹⁹ cm⁻³. The temperature dependence is calculated for m ^*_p =0.7 m₀ on the basis of these assumptions. The experimental dependences α₀=f(T) are used to determine the anisotropy of the hole effective masses. The maximum variation of (m ^*_p )_ε is observed in the <111> direction, and the minimum variation in the <100> direction.