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