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As the architecture of logic devices is evolving towards gate-all-around (GAA) structure, research efforts on advanced transistors are increasingly desired. In order to rapidly perform accurate compact modeling for these ultra-scaled transistors with the capability to cover dimensional variations, neural networks are considered. In this paper, a compact model generation methodology based on artificial neural network (ANN) is developed for GAA nanosheet FETs (NSFETs) at advanced technology nodes. The DC and AC characteristics of GAA NSFETs with various physical gate lengths (Lg), nanosheet widths (Wsh) and thicknesses (Tsh), as well as different gate voltages (Vgs) and drain voltages (Vds) are obtained through TCAD simulations. Subsequently, a high-precision ANN model architecture is evaluated. A systematical study on the impacts of ANN size, activation function, learning rate, and epoch (the times of complete pass through the entire training dataset) on the accuracy of ANN models is conducted, and a shallow neural network configuration for generating optimal ANN models is proposed. The results clearly show that the optimized ANN model can reproduce the DC and AC characteristics of NSFETs very accurately with a fitting error (MSE) of 0.01. [ABSTRACT FROM AUTHOR]

The complementary field-effect transistor (CFET) with stacked N-type FET (NFET) and P-type FET (PFET) is an attractive approach to shrink the footprint of multiple devices at circuit level and increase transistor density. Compared with traditional device structure, the unique geometry of CFET brings very different parasitics. In this work, we take the inverter as an exemplar CFET circuit building block and provide analytical compact models of calculating parasitic capacitance, which is critical to enable fast and accurate simulations at circuit level. The validity of the models is calibrated and verified with 3-D numerical simulations. A comparison between the CFET inverter with its same ground-rule gate-all-around FET (GAAFET) counterpart reveals the critical CFET design parameters and demonstrates performance advantage of CFET architecture. [ABSTRACT FROM AUTHOR]

Organic superlattices, consisting of alternating thin films of different organic molecules, are expected to provide new molecule assembly and unique properties that are applicable to advanced optoelectronic devices. Adopting organic superlattice as the structure of active layer may be an appropriate trade-off between planar heterojunctions and bulk heterojunction. With this structure, exciton diffusion efficiency and carrier mobility can be appropriately improved at the same time, leading to the optimization of device performance. In this paper, superlattice organic photodiodes based on heterojunction composed of C60 and zinc phthalocyanine were fabricated and characterized. We demonstrate good optoelectronic properties of these devices with superlattice structure through experimental data. It is found that the performances of the devices are strongly dependent on the incident optical power and the number of heterojunction periods, n. We optimized n and obtained high-responsive devices. The SL-OPD with n = 3 exhibits the photoresponsivity up to 5.21 (± 0.26) A W−1 at the incident optical intensity of 0.068 (± 0.003) mW cm−2. [ABSTRACT FROM AUTHOR]

Iridium complexes are widely used in dye phosphorescent guest-host systems which usually as emission layer of efficient organic light-emitting diodes. Phosphorescent organic light-emitting diodes (OLEDs) with tris(2-phenylpyridine) iridium [Ir(ppy) 3 ] as emissive dopant exhibited high internal quantum efficiency. N, N-diphenyl-N, N-bis(1-naphthylphenyl)-1,1-biphenyl-4,4-diamine (NPB) is a good candidate of host for guest–host system in OLEDs. It is significant that understanding and engineering of charge transport in Ir(ppy) 3 doped NPB films to design and optimize OLEDs, even organic lasers. In this paper, hole mobility and conductance of Ir(ppy) 3 doped NPB films were investigated by admittance spectroscopy. The results show that for a given applied voltage, with the doping concentration increasing, the conductance first increase reaching a maximum then decrease, which indicate that light doping of NPB with Ir(ppy) 3 weakly improves, while heavy doping deteriorates the conductivity. We found that light doping of NPB with Ir(ppy) 3 almost do not alter the hole mobility, which coincides with the previous theory. It is concluded that for films thinner than 300 nm, the electric field dependence of hole mobility is negative, that is, the mobility decrease, rather than increase, near exponentially with the square root of the electric field. [ABSTRACT FROM AUTHOR]