Faraday Rotation in ZnO: Determination of the Electron Effective Mass

The electron effective mass in ZnO has been determined from free-carrier Faraday rotation. A value of $0.24m_0$ is obtained for the high-frequency band mass, giving a value of $0.29m_0$ for the low-frequency polaron mass. The free-carrier Faraday rotation in a polar compound is well described by a simple Drude theory, although polaron corrections may be important to other optical properties. The interband Faraday rotation in ZnO agrees with theoretical models assuming direct transitions between parabolic valence and conduction bands.