Vertically-Aligned Indium Nitride Nanorod Arrays as Bright Terahertz Emitter

The physical properties of vertically-aligned Indium Nitride (InN) nanorod arrays grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy in terahertz (THz) spectral range has been elucidated by terahertz time-domain spectroscopy (THz-TDS) and their application as the efficient THz emitter has been investigated. The key parameters that determine the free carrier dynamics of the InN nanorods are extracted by applying a modified Drude model, which includes the scattering effect of electrons along the boundary of nanorods, while those of InN film are obtained by the Drude model. Due to the large surface areas provided by the sidewalls of nanorods, more than ten times of THz intensity enhancement compared to InN film is obtained for photoexcited InN nanorod array through the photo-Dember effect. However, the power enhancement is selectively depending on the size of the nanorods with respect to the thickness of surface accumulation layer.