Physics-based analysis of low frequency drain noise-current in AlxGa1−xN/GaN HFETs

Abstract

A physics-based theoretical model for the low frequency drain noise-current characteristics of AlGaN/GaN heterojunction field effect transistors (HFETs) is developed based on the number fluctuation noise theory. Founded on the calculation of the ground and first excited subband energy levels of the two-dimensional electron gas (2DEG) at an AlGaN/GaN heterointerface using the variational method, the model incorporates both tunnelling and thermally activated processes of trapping/de-trapping of the 2DEG carriers into and out of the trap sites of the barrier and buffer layers. It is found that the thermally activated process is dominant in the frequency range where a 1/f2 bulge signature is observed, whereas the tunnelling mechanism is dominant in the frequency range where a 1/f spectrum supersedes. A dominant trap level in the buffer layer, which is responsible for the 1/f2 bulge signature, is estimated by fitting the model with temperature-dependent experimental observations. The theoretical results are in good agreement with experimental data.