Improvement of Terahertz Wave Radiation for InAs Nanowires by Simple Dipping into Tap Water

Abstract

We report improvement of terahertz (THz) wave radiation for Si-based catalyst-free InAs nanowires (NWs) by simple dipping into tap water (DTW). In addition, the possibility of using InAs NWs as a cost-effective method for biomedical applications is discussed by comparison to bulk InAs. The peak-to-peak current signals (PPCSs) of InAs NWs measured from THz time-domain spectroscopy increased with increasing NW height. For example, the PPCS of 10 μm-long InAs NWs was 2.86 times stronger than that of 2.1 μm-long NWs. The THz spectra of the InAs NWs obtained by applying a fast Fourier transformation to the current signals showed a main frequency of 0.5 THz, which can be applied to a variety of medical imaging systems. After the DTW process, structural variation was not observed for 2.1 μm-long InAs NWs. However, the top region of several InAs NWs with heights of 4.6 and 5.8 μm merged into a conical structure. InAs NWs with a height of 10 μm resulted in a bundle feature forming above the conical shape, where the length of bundle region was 4 μm. After the DTW process, the PPCS for 10 μm-long InAs NWs increased by 15 percent compared to that of the as-grown case.

Anodically Induced Chemical Etching of GaAs Wafers for a GaAs Nanowire-Based Flexible Terahertz Wave Emitter

“…THz waves generated from GaAs NWs are more intense compared to those from bulk GaAs. GaAs NWs feature high electron mobility and short charge carrier lifetimes compared to the bulk GaAs wafer. , In addition, the spatial distance between electrons and holes could be increased with extending length of the GaAs NWs, resulting in an increase of the dipole strength within a certain range . We have experimentally confirmed that a THz wave is strongly generated 7.5 times more in the GaAs NWs with a length of 32 μm than the bulk GaAs substrate.…”

“…51,57 In addition, the spatial distance between electrons and holes could be increased with extending length of the GaAs NWs, resulting in an increase of the dipole strength within a certain range. 55 We have experimentally confirmed that a THz wave is strongly generated 7.5 times more in the GaAs NWs with a length of 32 μm than the bulk GaAs substrate.…”

“…As far as we know, all previous GaAs NWs employed to investigate the generation of THz waves were fabricated by bottom-up methods. However, the conventional bottom-up methods do not allow tight control of the crystallographic orientation, aspect ratio, and growth position and morphology of GaAs NWs. − To verify the emission property of a THz wave from AICE-formed GaAs NWs, we have conducted THz time domain emission spectroscopy with extended arrays of NW samples with various lengths and morphologies.…”

Recent advances in THz detectors based on semiconductor structures with quantum confinement: a review

“…Despite nanowires (or nanothreads) are widely used in various THz applications and exploited as THz emitters [100][101][102] and detectors [103][104][105], almost none of them utilize quantum confinement properties. The main problem is the unfeasibility of reliable fabrication of 1D planar structures with nm scale using the existent semiconductor fabrication technology to provide quantum confinement.…”

Pulsed THz emission from wurtzite phase catalyst-free InAs nanowires

“…NWs of InN [8], silicon [9], GaInAs and GaAsSb [10,11], germanium [12], InP [13], and GaAs [14]. Several groups have also studied the NWs from InAs [15][16][17] because the bulk crystals of this narrow gap semiconductor are the most efficient THz emitters [2]. It has been found that the average THz power emitted by InAs NWs is higher in longer nanowires and it is saturating when their length exceeds 5 µm [16].…”