Photoconductivity, carrier lifetime and mobility evaluation of GaAs films on Si (100) using optical pump terahertz probe measurements

The carrier lifetimes and electron mobility values were estimated for 2 μm thick GaAs films grown on Si (100) substrates by means of optical pump terahertz probe (OPTP) technique. The GaAs/Si films measured were epitaxial grown at different substrate temperatures (T _S = 520 °C or T _S = 630 °C). From x-ray diffraction measurements and Raman spectroscopy, the GaAs/Si films were shown to experience minimum strain at room temperature, and crystal misorientation in the (111) or (110) direction. With no measureable photoluminescence at room temperature, carrier lifetimes were measured via OPTP and found to be ∼20 and ∼35 ps for a fluence of ∼4 μJ cm⁻², which is in the same order of magnitude as a reference bulk GaAs grown on SI–GaAs (T _S = 630 °C) having a lifetime of ∼70 ps. From OPTP photoconductivity measurements, the estimated GaAs/Si films' electron mobility are ∼2900 cm² V⁻¹ s⁻¹ (T _S = 520 °C) and ∼3500 cm² V⁻¹ s⁻¹ (T _S = 630 °C) at a pump-probe delay time of Δt = 50 ps, in which the bulk GaAs electron mobility is ∼5200 cm² V⁻¹ s⁻¹. (paper)