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

Abstract

AlGaN/GaN Fin-shaped field-effect transistors (FinFETs) with nano-sized Fin width ( $\text{W}_{\mathrm {Fin}}$ ) 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 ( $\text{W}_{\mathrm {Fin}}$ = 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 ( $N_{t}$ ) 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 ( $\alpha _{\mathrm {H}}$ ) 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} \times $ frequency ( $f$ )) versus $\text{I}_{\mathrm {d}}$ curves, the volume accumulation phenomenon is also clearly observed in narrow Fin device.

Keywords

• AlGaN/GaN FinFET
• fin width
• low-frequency noise
• bulk conduction
• volume accumulation