Pulsed terahertz time domain spectroscopy of vertically structured photoconductive antennas.
APPL PHYS LETT
, Article 081106. 10.1063/1.3313940.
We present a terahertz (THz) photoconductive emitter structure, which employs a n-doped layer underneath a low-temperature-grown GaAs region to enable the THz transient to couple vertically through a defined mesa. A nonlinear bias dependence is observed, yielding an order in magnitude improvement in power for a mesa device with a 100 mu m(2) area over a conventional planar control reference device at 32 V and 5 mW illumination power. We relate the bias dependence of the THz signal to the breakdown voltage observed in the current-voltage characteristic. Reducing the antenna gap size through reducing the thickness of the low temperature-GaAs region below 1 mu m shows a large improvement in the bandwidth of the device, with an enhancement of the normalized intensity between 0.2 to 2 THz for a bow-tie antenna geometry.
|Title:||Pulsed terahertz time domain spectroscopy of vertically structured photoconductive antennas|
|Keywords:||antennas, gallium arsenide, III-V semiconductors, photoconducting materials, semiconductor doping, TEMPERATURE-GROWN GAAS|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Engineering Science
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