Experimental Investigation of Conduction Band of GaSb

The conduction band of GaSb was investigated by making the following measurements on a number of $n$-type samples with different carrier concentrations: (1) Hall effect and conductivity between 1.5°K and 370°K; (2) the change of resistance and Hall effect of the samples under hydrostatic pressure (up to 14×${10}^9$ dynes/${\mathrm{cm}}^2$) at room temperature; and (3) the change of resistance due to uniaxial stress between 77°K and 370°K. Our data can be explained on the basis of a double conduction band for this material with the lowest band-minimum in the center of the Brillouin Zone characterized by spherical constant-energy surfaces and the next minima along [111] directions in $k$-space characterized by ellipsoidal constant-energy surfaces. Our data can be further interpreted by assuming that the deformation potentials for the two bands in GaSb are similar to those of the corresponding bands in $n$-type germanium. The energy separation of the two bands at room temperature is estimated to be about 0.08 ev. The observed temperature dependence of the piezoresistance could be explained by assuming that the energy separation $\Delta E$ changes with temperature at a rate $\left(\frac{d\Delta E}{\mathrm{dT}}\right)\approx -3\mathrm{}\times {10}^{-4\mathrm{}}$ ev/°C. Throughout the analysis, the relaxation times for the electrons in the two bands were assumed to be independent of energy.