Abstract-Terahertz Spectroscopy of Thermal Radiation from AlGaN/GaN Heterostructure on Sapphire at Low Temperatures

Ignas Grigelionis and Irmantas Kašalynas

https://res.mdpi.com/d_attachment/applsci/applsci-10-00851/article_deploy/applsci-10-00851.pdf

Terahertz spectroscopy of thermal radiation from electrically pumped AlGaN/GaN
structures on sapphire substrate was investigated in this work. Comparison of experimental THz spectroscopy results to theoretical spectra calculations shows that thermal radiation of the sample lattice is the main mechanism causing the emission above T = 155 K, and it is mainly influenced by sapphire substrate. Here, the emission was attributed to the radiative electron transitions in shallow impurities and nitrogen vacancies as well as to radiative decay of longitudinal optical phonons (387 cm−1) in sapphire substrate. We have successfully demonstrated that THz emission spectroscopy can be used to define the temperature at which thermal emission from AlGaN/GaN HEMT structures dominates the emission spectrum.

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.