Variation of Electrical Properties with Zn Concentration in GaP

The resistivity and Hall coefficient R_H 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 N_Zn, 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 2.1×10¹⁹ cm⁻³. The low‐concentration region is observed for $N_{\mathrm{Zn}}{\text{≲2.0×10}}^{17}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ , the intermediate‐concentration region for ${\text{2.0×10}}^{17}{\mathrm{\lesssim N}}_{\mathrm{Zn}}{\text{≲2.1×10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ , and the high‐concentration region for $N_{\mathrm{Zn}}{\text{≳2.1×10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ . In the intermediate‐concentration region the high‐temperature hole concentration, determined from p=1/eR_H, 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.