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Improving the dynamic range of InGaAs-based THz detectors by localized beryllium doping: up to 70  dB at 3  THz

: Kohlhaas, R.B.; Dietz, R.J.B.; Breuer, S.; Nellen, S.; Liebermeister, L.; Schell, M.; Globisch, B.


Optics Letters 43 (2018), No.21, pp.5423-5426
ISSN: 0146-9592
Journal Article
Fraunhofer HHI ()

In this Letter, we report on photoconductive terahertz (THz) detectors for 1550 nm excitation based on a low-temperature-grown InGaAs/InAlAs superlattice with a localized beryllium doping profile. With this approach, we address the inherent lifetime-mobility trade-off that arises, since trapping centers also act as scattering sites for photo-excited electrons. The localized doping of the InAlAs barrier only leads to faster electron trapping for a given mobility. As a result, we obtain THz detectors with more than 6 THz bandwidths and 70 dB dynamic ranges (DNRs) at 3 THz and 55 dB DNR at 4 THz. To the best of our knowledge, this is the highest DNR for photoconductive THz time-domain spectroscopy systems published so far.