Variation of Electrical Properties with Zn Concentration in GaP

• Published in: Journal of applied physics 1969-01, Vol.40 (7), p.2945-2958
• Main Authors: Casey, H. C., Ermanis, F., Wolfstirn, K. B.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1658106

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 2.1×1019 cm−3. The low-concentration region is observed for NZn≲2.0×1017 cm−3, the intermediate-concentration region for 2.0×1017≲NZn≲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.