Compositional Engineering of Cu-Doped SnO Film for Complementary Metal Oxide Semiconductor Technology.

Metal oxide semiconductor (MOS)-based complementary thin-film transistor (TFT) circuits have broad application prospects in large-scale flexible electronics. To simplify circuit design and increase integration density, basic complementary circuits require both p- and n-channel transistors based on an individual semiconductor. However, until now, no MOSs that can simultaneously show p- and n-type conduction behavior have been reported. Herein, we demonstrate for the first time that Cu-doped SnO (Cu:SnO) with HfO2 capping can be employed for high-performance p- and n-channel TFTs. The interstitial Cu+ can induce an n-doping effect while restraining electron-electron scatterings by removing conduction band minimum degeneracy. As a result, the Cu3 atom %:SnO TFTs exhibit a record high electron mobility of 43.8 cm2 V-1 s-1. Meanwhile, the p-channel devices show an ultrahigh hole mobility of 2.4 cm2 V-1 s-1. Flexible complementary logics are then established, including an inverter, NAND gates, and NOR gates. Impressively, the inverter exhibits an ultrahigh gain of 302.4 and excellent operational stability and bending reliability.

Interlayer Transition Induced Infrared Response in ReS2/2D Perovskite van der Waals Heterostructure Photodetector.

The emerging Ruddlesden-Popper two-dimensional perovskite (2D PVK) has recently joined the family of 2D semiconductors as a potential competitor for building van der Waals (vdW) heterostructures in future optoelectronics. However, to date, most of the reported heterostructures based on 2D PVKs suffer from poor spectral response that is caused by intrinsic wide bandgap of constituting materials. Herein, a direct heterointerface bandgap (∼0.4 eV) between 2D PVK and ReS2 is demonstrated. The strong interlayer coupling reduces the energy interval at the heterojunction region so that the heterostructure shows high sensitivity with the spectral response expanding to 2000 nm. The large type-II band offsets exceeding 1.1 eV ensure fast photogenerated carriers separation at the heterointerface. When this heterostructure is used as a self-driven photodetector, it exhibits a record high detectivity up to 1.8 × 1014 Jones, surpassing any reported 2D self-driven devices, and an impressive external quantum efficiency of 68%.

Two-Dimensional Perovskite-Gated AlGaN/GaN High-Electron-Mobility-Transistor for Neuromorphic Vision Sensor.

The extraordinary optoelectronic properties and continued commercialization of GaN enable it a promising component for neuromorphic visual system (NVS). However, typical GaN-based optoelectronic devices demonstrated to data only show temporary and unidirectional photoresponse in ultraviolet region, which is an insurmountable obstacle for construction of NVS in practical applications. Herein, an ultrasensitive visual sensor with phototransistor architecture consisting of AlGaN/GaN high-electron-mobility-transistor (HEMT) and two-dimensional Ruddlesden-Popper organic-inorganic halide perovskite (2D OIHP) is reported. Utilizing the significant variation in activation energy for ion transport in 2D OIHP (from 1.3 eV under dark to 0.4 eV under illumination), the sensor can efficiently perceive and storage optical information in ultraviolet-visible region. Meanwhile, the photo-enhanced field-effect mechanism in the depletion-mode HEMT enables gate-tunable negative and positive photoresponse, where some typical optoelectronic synaptic functions including inhibitory and excitatory postsynaptic current as well as paired-pulse facilitation are demonstrated. More importantly, a NVS based on the proposed visual sensor array is constructed for achieving neuromorphic visual preprocessing with an improved color image recognition rate of 100%.

Flexible SnO Optoelectronic Memory Based on Light-Dependent Ionic Migration in Ruddlesden-Popper Perovskite.

Nonvolatile optoelectronic memories based on organic-inorganic hybrid perovskites have appeared as powerful candidates for next-generation soft electronics. Here, ambipolar SnO transistor-based nonvolatile memories with multibit memory behavior (11 storage states, 120 nC state-1) and ultralong retention time (>105 s) are demonstrated for which an Al2O3/two-dimensional Ruddlesden-Popper perovskite (2D PVK) heterostructure dielectric architecture is employed. The unique storage features are attributed to suppressed gate leakage by Al2O3 layer and hopping-like ionic transport in 2D PVK with varying activation energy under different light intensities. The photoinduced field-effect mechanism enables top-gated transistor operation under illumination, which would not be achieved under dark. As a result, the device exhibits remarkable photoresponsive characteristics, including ultrahigh specific detectivity (2.7 × 1015 Jones) and broadband spectrum distinction capacity (375-1064 nm). This study offers valuable insight on the PVK-based dielectric engineering for information storage and paves the way toward multilevel broadband-response optoelectronic memories.