Effects of Pressure on the Electrical Properties of Semiconductors

Measurements have been made of the effects of hydrostatic pressures between one and 2000 atmospheres on the electrical properties of several different semiconductors. The materials studied are germanium, indium antimonide, indium arsenide, gallium antimonide, tellurium, and magnesium stannide. It has been found that the temperature at which the Hall coefficient of $p$-type Ge reverses sign shifts to a higher value under the application of a pressure of 2000 atmospheres, and that the magnitude of the shift is in good agreement with the shift predicted by the known increase of the energy gap from one to 2000 atmospheres. The transverse magnetoresistance of InSb is found to decrease slightly with increasing pressure in accordance with the known decrease of electron mobility. Conductivity and Hall coefficient $\mathrm{vs}$ pressure measurements on extrinsic $n$-type samples of InAs and GaSb show that the electron mobility in InAs decreases by about 7 percent from one to 2000 atmospheres and that there is no such mobility change in GaSb. Conductivity and Hall coefficient $\mathrm{vs}$ pressure measurements on Te indicate that the energy gap is smaller by 0.032 ev at 2000 atmospheres than its value of about 0.336 ev at atmospheric pressure, and that the hole and electron mobilities increase with increasing pressure. A consistent scheme of interpretation of the results of the various pressure experiments on tellurium is proposed. Conductivity $\mathrm{vs}$ pressure measurements on ${\mathrm{Mg}}_2$Sn show that the energy gap widens with increasing pressure by roughly 0.01 ev between one and 2000 atmospheres.