Study on plasma instability of nonuniform two-dimensional electron gas

The plasma instability of two-dimensional electron gas (2DEG) is a crucial physical mechanism of generating terahertz radiation in high electron mobility transistors. In this paper, a new theoretical model is presented to study the plasma wave excitation in nonuniform 2DEGs. By using the auxiliary function and Wenzel-Kramers-Brillouin (WKB) approximation method, the general solution of plasma waves is obtained. On this basis, combined with the Dyakonov-Shur instability's boundary conditions, the modified wave increment caused by the non-uniformity is gained, which proves that the negative gradient of electron concentration in the channel will attenuate the wave increment and decrease the plasmonic frequency.