Abstract-Free-space terahertz radiation from a LT-GaAs-on-quartz large-area photoconductive emitter

Free-space terahertz radiation from a LT-GaAs-on-quartz large-area photoconductive emitter

David R. Bacon, Andrew D. Burnett, Matthew Swithenbank, Christopher Russell, Lianhe Li, Christopher D. Wood, John Cunningham, Edmund H. Linfield, A. Giles Davies, Paul Dean, and Joshua R. Freeman

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-23-26986

We report on large-area photoconductive terahertz (THz) emitters with a low-temperature-grown GaAs (LT-GaAs) active layer fabricated on quartz substrates using a lift-off transfer process. These devices are compared to the same LT-GaAs emitters when fabricated on the growth substrate. We find that the transferred devices show higher optical-to-THz conversion efficiencies and significantly larger breakdown fields, which we attribute to reduced parasitic current in the substrate. Through these improvements, we demonstrate a factor of ~8 increase in emitted THz field strength at the maximum operating voltage. In addition we find improved performance when these devices are used for photoconductive detection, which we explain through a combination of reduced parasitic substrate currents and reduced space-charge build-up in the device.

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Abstract-Time-domain measurement of terahertz frequency magnetoplasmon resonances in a two-dimensional electron system by the direct injection of picosecond pulsed currents

Jingbo Wu1, Oleksiy Sydoruk2, Alexander S. Mayorov1, Christopher D. Wood1, Divyang Mistry1, Lianhe Li1, Edmund H. Linfield1, A. Giles Davies1 and John E. Cunningham1,a)
http://scitation.aip.org/content/aip/journal/apl/108/9/10.1063/1.4943173
1 School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
2 Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
a) Electronic email: j.e.cunningham@leeds.ac.uk
Appl. Phys. Lett. 108, 091109 (2016); http://dx.doi.org/10.1063/1.4943173

We have investigated terahertz (THz) frequency magnetoplasmon resonances in a two-dimensional electron system through the direct injection of picosecond duration current pulses. The evolution of the time-domain signals was measured as a function of magnetic field, and the results were found to be in agreement with calculations using a mode-matching approach for four modes observed in the frequency range above 0.1 THz. This introduces a generic technique suitable for sampling ultrafast carrier dynamics in low-dimensional semiconductor nanostructures at THz frequencies.