Final PhD Seminar-III-V Compound Semiconductor Nanowire Terahertz Detectors
Terahertz (THz) spectroscopy and imaging have been widely used for materials analysis, security screening, medical diagnostic, biology imaging and non-destructive testing. Photoconductive (Auston) switches based on ion beam modified or low temperature grown semiconductor materials, is one of the most commonly used techniques for THz detection in many THz spectroscopy systems. One-dimensional III-V compound semiconductor nanowires, with their direct and tunable band gap, high carrier mobility (close to that in bulk materials), and in contrast short carrier lifetime (typically sub-nanosecond) and thus a fast response time in the THz regime, have been considered as ideal alternatives to conventional bulk semiconductor materials for THz detection. Such nanowire-based detectors, taking advantages of the nano-scale size and ability to grow on Si substrates (to incorporate with CMOS electronics), show great promise as sub-wavelength elements for near-field THz imaging or as highly integrated components for on-chip THz spectrometer .
In this work we present the first demonstration of photoconductive THz detectors based on single III-V semiconductor nanowires (including GaAs/AlGaAs, InP, n+-i-n+ InP single nanowires) with comparable sensitivity to the conventional bulk THz detectors and a further tuneable detection bandwidth resulting from specific device geometry design, showing a great potential for developing of nanowire-based THz time-domain spectroscopy systems. The design, fabrication and characterisation of single nanowire THz detector will be presented to provide an insight into the correlation between the single nanowire THz device performance and the nanowire optoelectronic property/antenna design, for further improvement of the nanowire detector sensitivity and bandwidth.