Abstract-Terahertz time-domain spectroscopy of two-dimensional plasmons in AlGaN/GaN heterostructures

Applied Physics Letters

Daniil Pashnev, Tommi Kaplas, Vadym Korotyeyev, Vytautas Janonis, Andrzej Urbanowicz, Justinas Jorudas, Irmantas Kašalynas, 

THz waveforms measured after transmission through a cryostat without (reference) and with (SP1000F50) the sample and (b) corresponding FFT power spectra obtained using the time window tcut2$t_{\mathit{cut}2}$. (c) Transmission power spectrum T1(f)$T_1(f)$ found using the time window tcut2$t_{\mathit{cut}2}$ and tcut1$t_{\mathit{cut}1}$ providing data with (w/) and without (w/o) FP oscillations, respectively.

https://aip.scitation.org/doi/abs/10.1063/5.0014977

Two-dimensional plasmons were investigated by terahertz time domain spectroscopy observing experimentally the distinctive minima and inflection points in the transmission power amplitude and phase spectra, respectively. Gratings of different periods (600, 800, and 1000 nm) and filling factors (50 and 80%) were provided to the two-dimensional electron gas in AlGaN/GaN heterostructures in order to measure the plasmon dispersion and the coupling efficiency with THz radiation. Comparative analysis of experimental data revealed that the resonant plasmon features in the amplitude spectrum are related to those in the phase spectrum by a simple integral relation, paving the way for phase spectroscopy of the plasmon phenomena in fields of THz physics and engineering.

This work was supported by the Research Council of Lithuania (Lietuvos mokslo taryba) under the “TERAGANWIRE” Project (Grant No. S-LL-19-1).

Abstract-Terahertz electroluminescence of shallow impurities in AlGaN/GaN heterostructures at 20 K and 110 K temperature

Ignas Grigelionis, Justinas Jorudas, Vytautas Jakštas, Vytautas Janonis, Irmantas Kašalynas, Pawel Prystawko, Piotr Kruszewski, Michal Leszczyński,



https://www.sciencedirect.com/science/article/pii/S1369800118319425


Terahertz (THz) electroluminescence of shallow impurities in the AlGaN/GaN HEMT structures grown either on sapphire or silicon carbide substrates were studied in this work. The radiative electron transitions $2p-1s$ in the oxygen and silicon donors as well as additional $c-1s$ transitions in the carbon atoms also were identified by THz emission spectroscopy at the temperatures of 110 K and 20 K, respectively. Moreover, the thermal quenching effect of the THz electroluminescence signals was found to occur at much higher electrical powers that were injected in the HEMT structures grown on silicon carbide as compared to that grown on the sapphire substrate.