VARIATION OF ELECTRICAL PROPERTIES WITH ZN CONCENTRATION IN GAP

The resistivity and Hall coefficient RH for Zn-doped GaP were measured at temperatures between 4.2°and 775°K. Neutron activation and through diffusion with radioactive 65Zn were used to determine the Zn concentration NZn, which ranged from 6.7×1016 cm-3 to 2.1×1019 cm-3. At the lowest Zn concentration the thermal ionization energy for Zn in GaP was found to be 0.060±0.002 eV. The thermal ionization energy decreases rapidly for Zn concentrations in excess of 2.0×1017 cm-3. Metallic impurity conduction was observed at a Zn concentration of 2.1×10 19 cm-3. The low-concentration region is observed for NZn≲2.0×1017 cm-3, the intermediate-concentration region for 2.0×1017≲N Zn≲2.1×1019 cm-3, and the high-concentration region for NZn≳2.1×1019 cm-3. In the intermediate-concentration region the high-temperature hole concentration, determined from p=1/eRH, was found to exceed the Zn concentration by a significant amount. Analysis of the temperature-dependent hole concentration results in an effective density-of-states mass ratio of approximately 0.5. The lightest doped sample had a room-temperature Hall mobility of 120 cm2/V·sec and a maximum mobility of 2050 cm2/V·sec at 55°K. The maximum mobility at low temperature is limited by ionized and neutral impurity scattering, while the dominant high-temperature scattering mechanism appears to be optical phonon scattering. © 1969 The American Institute of Physics.