Effect of Stress on the Electrical Properties ofn-Type Gallium Arsenide

Abstract

The electrical resistivity and Hall coefficient of undoped $n$-type GaAs samples with room-temperature carrier concentrations between 1.9×${10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$ and 3.7×${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$ have been measured as a function of uniaxial compression (up to 2×${10}^8$ dyn/${\mathrm{cm}}^2$) at various temperatures between 77 and 298°K and as a function of hydrostatic pressure (up to 6×${10}^9$ dyn/${\mathrm{cm}}^2$) between 195 and 298°K. Some measurements were also made on two vanadium-doped samples. The results indicate that conduction takes place in a single band at k=0 and that the concentration $n$ and mobility $\mu$ of the carriers in this band decrease with increasing compressional stress, the rate of decrease of $n$ being much greater than that of $\mu$ in some cases. Between 195 and 298°K the conduction-electron concentration is explained quantitatively by the presence of non-shallow donors having a pressure-dependent ionization energy $E_I\approx [0.17+{10}^{-11\mathrm{}}{P}_{\mathrm{dyn}/{\mathrm{cm}}^2}]$ eV, as well as of shallow donors and acceptors. At lower temperatures the stress dependence of $n$ cannot be explained using the above nonshallow level but seems to imply the presence of a less deep, nonshallow level. The dependence of the mobility on pressure is accounted for in most cases by the variation of the electron effective mass with pressure. Impurity-level concentrations deduced from the electrical measurements, the nature of the nonshallow donors, and the role of vanadium impurity are discussed with the aid of mass-spectrographic analyses. Carbon, nitrogen, and oxygen seem to be likely sources of the 0.17-eV donor levels.