The electrical conductivity of InSb has been measured as a function of temperature from -78°C to +300°C and pressures up to 12 000 kg/${\mathrm{cm}}^2$. It is found that the activation energy increases at a rate 15.5×${10}^{-6\mathrm{}}$ ev/(kg/${\mathrm{cm}}^2$), that the electron mobility is approximately inversely proportional to the activation energy, and that the hole mobility is independent of pressure. On the basis of these mobility effects it is concluded that the $k$ of the valence band energy extremum is not zero. An examination of the effects of pressure and temperature above 200°C suggests that there are three or four equivalent energy minima in the conduction band.

• Received 28 March 1955

DOI:https://doi.org/10.1103/PhysRev.99.490