Optical properties

Excitation of terahertz radiation in $p$–$n$-heterostructures based on $a$-Si:H/$c$-Si

A. V. Andrianov^a, A. N. Aleshin^a, S. N. Abolmasov^ab, E. I. Terukov^acb, A. O. Zahar'in<sup>a

a</sup> Ioffe Institute, St. Petersburg, Russia
^b R&D Center TFTE, St. Petersburg, Russia
^c Saint Petersburg Electrotechnical University "LETI", St. Petersburg, Russia

Abstract: Studies on the generation of terahertz (THz) radiation in $p$–$n$-heterostructures based on $a$-Si:H/$c$-Si upon their photoexcitation by a femtosecond titanium-sapphire laser with a wavelength of 800 nm are presented. The properties of observed THz radiation allow to explain its nature by excitation of fast photocurrent of nonequilibrium charge carriers created in the region of the potential barrier under femtosecond interband photoexcitation of the structure. The fast photocurrent, in turn, emits THz electromagnetic waves. The waveforms and amplitude spectra of the observed THz radiation reflect the dynamics of photoexcited charge carriers in the structures. The intensity of THz radiation observed in the studied $p$–$n$-heterostructures based on $a$-Si:H/$c$-Si is comparable to that generated in $n$-InAs crystals, which are widely used as emitters in systems of THz time-domain spectroscopy. Therefore, $a$-Si:H/$c$-Si $p$–$n$-heterostructures can be used as THz emitters for need of THz spectroscopy.

Keywords: femtosecond laser photoexcitation, heterostructures, fast photocurrent, terahertz electromagnetic radiation.

Received: 02.03.2023
Revised: 02.03.2023
Accepted: 13.03.2023

DOI: 10.21883/FTT.2023.05.55503.27

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