Impact of Fin Width on Low-Frequency Noise in AlGaN/GaN FinFETs: Evidence for Bulk Conduction

AlGaN/GaN Fin-shaped field-effect transistors (FinFETs) with nano-sized Fin width (W-Fin) from 20 nm to 230 nm are characterized using low-frequency noise (LFN) measurement. All devices exhibit 1/f noise shape with Hooge mobility fluctuations (HMF) at subthreshold region and carrier number fluctuations (CNF) at accumulation region. However, the lowest normalized drain current noise spectral densities (S-Id /I-d(2)) are obtained in the narrow Fin device (W-Fin = 20 nm). This is due to significant contribution of bulk channel without the 2-dimensional electron gas density (2DEG) channel and two sidewall metal-oxide-semiconductor (MOS) channels. It is also noticed that the lowest trap density (Nt) and a large separation in CNF noise model clearly indicate to the volume accumulation effect caused by bulk conduction in narrow device. The Hooge constants (aH) extracted by HMF noise model for the narrow device are one-order higher than those of the wide Fin device, which tells that the narrow device suffers from the strong phonon scattering in the bulk channel. From the product of (S-Id x frequency (f )) versus Id curves, the volume accumulation phenomenon is also clearly observed in narrow Fin device.