Noncontact Characterization of Carrier Mobility in Long-Wave Infrared HgCdTe Films With Terahertz Time-Domain Spectroscopy

We use terahertz time-domain spectroscopy to measure the complex dielectric function of long-wave infrared Hg 1-x Cd x Te films (x = 0.18, 0.20, 0.22) as a function of temperature in a non-contact manner. Using a Drude-Lorentz model fit to the measured complex transmission function combined with a Kane model description of the band structure, we obtain the temperature-dependent conduction band carrier density, effective mass, scattering time and carrier mobility for all three Hg 1-x Cd x Te films. The optical properties of a bare substrate of Cd 0.96 Zn 0.04 Te were also measured in the terahertz region. The high quality of the Hg 1-x Cd x Te films is demonstrated by ultrahigh mobilities exceeding 10 5 cm 2 V -1 s -1 and ionized donor densities less than 3 × 10 15 cm -3 at temperatures below 100 K.