Determination of carrier concentration dependent electron effective mass and scattering time of n-ZnO thin film by terahertz time domain spectroscopy

J. Tang1,2, L. Y. Deng1, C. B. Tay1,2, X. H. Zhang3, J. W. Chai3, H. Qin4, H. W. Liu5, T. Venkatesan2 and S. J. Chua1,2,3,a)

Abstract

We demonstrated a novel and widely accessible method for determining the electron effective mass and scattering time of ZnO films with different carrier concentrations by combiningterahertz time-domain spectroscopy with Hall measurement. The terahertz time domain spectroscopy (THz-TDS) transmission spectra (0.1–2THz) were well described by Drude model. It is found that electron effective mass varied from 0.23m0 to 0.26m0 as the electron concentration changes from 5.9 × 10¹⁷ cm⁻³ to 4.0 × 10¹⁹ cm⁻³. The carrier concentrationdependent characteristic is ascribed to the non-parabolicity of conduction band. Free carrier localization mechanism explained the discrepancy in mobilities obtained from THz-TDS and Hall measurements.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://scitation.aip.org/content/aip/journal/jap/115/3/10.1063/1.4861421