Physics-based modeling and characterization of low frequency noise behavior for AlxGa1−xN/GaN HEMT

Abstract

A physics-based low frequency noise (LFN) model for AlxGa1−xN/GaN high electron mobility transistors (HEMTs) is proposed in this article. By treating the distributed low-density surface donor states as the responsible mechanism and exhibiting charge neutrality in combination with the electric field across the barrier layer, a compact expression for Schottky barrier height (SBH) capturing the physics behind the variations of AlxGa1−xN layer thickness is profiled, which incorporates the effect of strain relaxation caused by high Al fraction. Furthermore, the SBH is applied to develop VTH and IDS. The LFN model, dominated by the fluctuations of carriers and drain current in the channel caused by the trapping/detrapping process, is subsequently obtained. It is indicated that the larger threshold voltage, higher drain current, and normalized noise are observed by our model with respect to the traditional SBH expressed only by an interpolated linear function of x. The drain current noise behavior showing the 1/f spectrum down to very low frequencies is seriously subjected to the barrier thickness-dependent SBH of AlxGa1−xN/GaN HEMTs. The accuracy of the proposed model is also verified by comparison with the experimental results from different devices.