We investigated the performances of GaN junctionless fin-shaped field-effect transistors (FinFETs) with two different types of gate structures; overlapped-and partially covered-gate. DC, low-frequency noise (LFN), and pulsed I-V characterization measurements were performed and analyzed together in order to identify the conduction mechanism and examine both the interface and buffer traps in the devices. The fabricated GaN junctionless device with overlapped-gate structure exhibits improved DC and noise performance compared to the device with partially covered-gate, even though its gate length is much larger. The LFN behavior was found to be dominated by carrier number fluctuations (CNF). At off-state, the device with partially covered-gate exhibits generation-recombination (g-r) noise on top of 1/f noise. This superposition is correlated with the severe current collapse revealed by pulsed I-V measurements. In contrast, the device with overlapped-gate shows clear 1/f behavior without g-r noise.

This article presents a new methodology for the extraction of low-frequency noise (LFN) or random telegraph noise (RTN) parameters, such as the gate oxide interface trap density, Nt, and the mobility fluctuations factor, Ω , without the influence of the source/drain series resistance, Rsd. The method utilizes the Y-function--which is immune to any first-order degradation, including the series resistance--as well as the intrinsic mobility degradation factors θ1,0 and θ₂. The proposed extraction technique is first demonstrated through numerical calculations and then applied on experimental results of n-channel short length FinFETs. It is shown that if the Rsd impact is not accounted for, the extracted LFN parameters through the classic carrier number fluctuations (CNF) with correlated mobility fluctuations (CMF) model can lead to significant extraction errors. This mainly concerns the correlated mobility factor Ω, which may be strongly underestimated, but also the extraction of the trap density Nt.

GaN-based materials are expected to show excellent immunity against short-channel effects because they have relatively lower permittivity and higher electron effective mass, compared to other materials such as Si, Ge, and In(Ga)As. To further reduce the short-channel effects, it is important to enhance the gate controllability of the device by utilizing a gate-all-around (GAA) structure. In this article, GaN vertical GAA nanowire MOSFETs with various diameters of 120, 75, and 45 nm have been fabricated. The device with a diameter of 120 nm shows a threshold voltage of 0.7 V, drain saturation voltage of 0.5 V, and subthreshold swing of 70 mV/decade, which would be suitable for low-voltage/power applications. However, the devices with smaller diameters of 75 and 45 nm show peculiar characteristics, such as a second rise of the drain current in output characteristics and a negative transconductance.

Field effect transistors (FETs) based on networks of randomly oriented Si nanowires (Si nanonets or Si NNs) were biomodified using Thrombin Binding Aptamer (TBA–15) probe with the final objective to sense thrombin by electrical detection. In this work, the impact of the biomodification on the electrical properties of the Si NN–FETs was studied. First, the results that were obtained for the optimization of the (3-Glycidyloxypropyl)trimethoxysilane (GOPS)-based biofunctionalization process by using UV radiation are reported. The biofunctionalized devices were analyzed by atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM), proving that TBA–15 probes were properly grafted on the surface of the devices, and by means of epifluorescence microscopy it was possible to demonstrate that the UV-assisted GOPS-based functionalization notably improves the homogeneity of the surface DNA distribution. Later, the electrical characteristics of 80 devices were analyzed before and after the biofunctionalization process, indicating that the results are highly dependent on the experimental protocol. We found that the TBA–15 hybridization capacity with its complementary strand is time dependent and that the transfer characteristics of the Si NN–FETs obtained after the TBA–15 probe grafting are also time dependent. These results help to elucidate and define the experimental precautions that must be taken into account to fabricate reproducible devices.