Defect-related temperature dependence of THz emission from GaAs/AlGaAs MQWs grown on off- and on-axis substrates

Abstract

Simultaneous molecular beam epitaxial growth of GaAs/AlGaAs multiple quantum wells on two different substrates (one on GaAs (100) and another on a GaAs substrate misoriented by 4° in the (111) direction) resulted in samples of similar structure, but having different defect profiles. The on-axis sample had a higher defect density and more types of electron traps than the off-axis counterpart. Temperature-dependent terahertz (THz) emission and temperature-dependent photoluminescence were measured; in both cases, an intensity quenching was observed between 75 K – 250 K for the on-axis sample, but not in the off-axis sample. We attribute the THz emission quenching to the electron traps present in the sample, which decreases the photocarriers participating in setting up the surface field.

Enhanced THz emission from spintronic Fe/Pt emitters through crystal growth optimization

“…The parameter of elastic electron scattering lifetime was used to parametrize the overall defect density 8 . In an analogy to the dependence of photocurrents and THz emission on defect density in semiconducting materials 25 , the defect engineering through the proper choice of substrates, promoting epitaxial FM layers, as well as through modification of the Fe-Pt interface quality, altered dramatically the emitted THz characteristics 8 .…”