Compressive and tensile strain effects on the ultrafast carrier dynamics and transport of gallium arsenide thin films on silicon and magnesium oxide substrates

Abstract

We investigate strain effects on the ultrafast carrier dynamics and transport of gallium arsenide films on silicon (GaAs/Si) and magnesium oxide (GaAs/MgO) substrates using temperature-dependent photoluminescence (PL) and terahertz time-domain spectroscopy (THz-TDS) from 11 K - 300 K. The PL shows that GaAs/Si and GaAs/MgO samples are under tensile and compressive strain at low temperature, respectively. The temperature-dependent THz emission from GaAs/Si does not show significant differences with the emission from bulk GaAs, while the THz emission from GaAs/MgO shows an order-of-magnitude decrease at low temperature. The THz emission from the samples exhibits an interplay between strain-induced effective mass changes and temperature-dependent electric field effects.