We present investigations of the fin-shaped GaN/AlGaN field effect transistors with two lateral Schottky barrier gates exactly placed on the edges of the fin-shaped transistor channel. We call this kind of FinFET modification the EdgeFET. It allowed us to efficiently control the current flow in two-dimensional electron gas conduction channel. We present experimental data of sub-THz detection by EdgeFETs. Control of the side gates allows changing the width of two-dimensional electron gas and forming a wire, as we expect should be beneficial for observation of terahertz plasma wave resonances. This paves the way towards future terahertz optopair using high-quality factor plasma wave resonances, for which it is necessary to eliminate oblique modes. We report also on the high-voltage, noise, and radio frequency (RF) performances of aluminium gallium nitride/gallium nitride (AlGaN/GaN) on silicon carbide (SiC) devices without any GaN buffer. Such a GaN–SiC hybrid material was developed in order to improve thermal management and to reduce trapping effects should be beneficial for observation of resonant emission.
We report three approaches to development of electrically-pumped THz emitters based on III-Nitride structures. The first approach entails the investigation of two-dimensional (2D) plasmons in grating-gated AlGaN/GaN heterostructures performed at temperatures above liquid nitrogen by means of THz time-domain spectroscopy (TDS). Comparative analysis of the experimental data revealed the considerable phase shift of transmitted THz pulses at the resonant frequencies of collective oscillations of the grating-gated 2D electron gas (2DEG). The use of 2D plasmons is proposed for the development of tunable-frequency THz emitters with electrical control of the emission frequency, beam wave front and directivity. Another approach is based on the THz electroluminescence of shallow impurities such as oxygen and silicon in the standard AlGaN/GaN high electron mobility transistor (HEMT) structures. The surface plasmonphonon polaritons (SPPhP) in n-GaN grating are also considered for the development of electrically-pumped THz sources under thermal and electrical excitation of directive (coherent) radiation. We note that emission frequency can be governed either by gate voltage (2D plasmons) or structural design (SPPhP). All discussed methods are compared in terms of achieved quality factor, operating temperature and emitted power.
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