Enhancement of THz Radiation Intensity in Fe/Heavy-Metal Spintronic Emitters Epitaxially Grown on GaAs(001)

We explored THz emission from laser illuminated Fe/heavy-metal bilayer spintronic emitters grown epitaxially on top of GaAs(001) substrates. The fabricated emitters show an overall enhancement of the transient THz radiation compared to structures fabricated on insulating substrates. In addition, the THz amplitude shows strongly vertically off-set hysteretic behavior in varying magnetic field. We ascribe these observations to the interplay of several mechanisms including inverse spin Hall effect, optical rectification, Lorentz force and chemical bonding at the epitaxial Fe/GaAs(001) interface.