Study of optical properties of AlGaN/GaN/SiC heterostructures designed for terahertz emission

Nowadays scientific community looks intensively for new materials and physical phenomena that would help to progress the development of compact room temperature THz emitters. Gallium Nitride (GaN) offers a revolutionary breakthrough for next generation of high-power and high-frequency electronic components due to unique physical properties of material such as a wide bandgap, high breakdown voltage, good thermal conductivity, stability etc. [M.Shur Solid-State Electronics (2019); U.K. Mishra et. all IEEE Transactions on Microwave Theory and Techniques 46 p.756-761 (1998)]. In particular, GaN-based hetero-structures have received great attention and the improvement of epi-layers and interfaces quality is in progress [J.T.Chen et all. Applied Physics Letters 113, 041605 (2018)]. A new method for monitoring of shallow impurities in close to real-electronic-device AlGaN/GaN structures with two-dimensional electron gas has been recently proposed by our group [I. Grigelionis et all, Materials Science in Semiconductor Processing 93, p. 280-283 (2019)]. Electrons plasma oscillation and lattice vibrations in polar semiconductors and heterostructures are also widely investigated [N.Rahbany Appl. Phys. 114 p.053505 (2013)]. Wide bandgap semiconductors possesses large splitting between LO and TO phonon modes and their usage is very convenient for basic research of resonant modes and for THz generation [K. Požela et all Appl Phys. Lett. 105 p.091601 (2014)]. Weak and strong latice phonons coupling with plasmons in a metal grating have been observed in AlGaN/GaN/SiC structures [V.Janonis et all physica status solidi (b) 255, 1700498 (2018)].
Aim of this PhD project is investigation of reflection, absorption, and emission spectra of (i) shallow impurities and (ii) phonons-plasmons modes in the THz frequency range and Infrared (IR) band at temperatures ranging from 4 K to 400 K.
For more information, please contact the theme supervisor I. Kašalynas.