Low-Frequency Noise in InGaAs Nanowire MOSFETs

Sammanfattning: Low-frequency (LF) noise (1/f as well as random telegraph-signal (RTS) noise) measurements were performed on high-performance InGaAs nanowire (NW) metal-oxide-semiconductor field-effect transistors (MOSFETs). 1/f noise measurements at room temperature (RT) show that the dominant noise mechanism is carrier number fluctuations. The minimum gate area normalized input gate voltage noise power spectral density (PSD) for these devices is as low as 80 µm^{2}µV^{2}Hz^{-1}, with a corresponding minimum trap density of 9·10 cm^{-3}eV^{-1}, where the calculation of the trap density bases on elastic tunneling of the channel electrons to and from the trap states in the gate oxide. These values are among the lowest for III-V MOSFETs, demonstrating the feasibility of a high-quality, low trap density, high-k gate oxide on InGaAs NW structures. 1/f noise measurements at low temperatures confirm that the dominant noise mechanism is carrier number fluctuations and also give some support for the elastic tunneling model. RTS noise signals were found in approximately 2/3 of the considered devices, indicating that very few traps influence the electron transport through the channel. It turns out that the capture and emission time constant of a single active trap state change with the applied gate bias. Different models (the elastic tunneling model and the Shockley-Read-Hall (SRH) model) are discussed to explain this behavior. Another striking feature of the RTS noise measurements is the large spread in the RTS noise amplitudes, with maximum amplitudes of up to 1 µA. Simulations of single trap induced subband fluctuations can reproduce this large spread, showing that the magnitude of the RTS noise amplitude is especially sensitive to the position of the trap state along the NW circumference. Temperature-dependent RTS noise measurements reveal a thermal activation of the time constants, which is inconsistent with elastic tunneling but can be explained by multi-phonon-assisted tunneling (inelastic tunneling).