Jianhong Yang

GaN-based hybrid-dimensional heterojunctions play a critical role in optoelectronics; however, their persistent photoconductivity (PPC)—essential for synaptic devices—has been limited to the UV regime by the wide bandgap of GaN. We report the photoconductive properties of dual-channel heterojunction devices composed of MoS2 and WSe2 integrated with GaN. Specifically, the GaN/WSe2 heterojunction did not exhibit a PPC effect under 633 nm light, while the GaN/MoS2 heterojunction displayed a pronounced PPC effect. Notably, the introduction of h-BN intercalation resulted in the GaN/h-BN/MoS2 heterojunction lacking the PPC effect. This paper analyzes the capture and excitation of carriers by CN defect states in GaN and demonstrates that the built-in electric field of the heterojunction influences the separation of photo-generated carriers, resulting in distinct PPC behaviors among various devices. Through h-BN intercalation, the pivotal role of interlayer interaction in extending the response wavelength of GaN-based optoelectronic synapses has been unambiguously identified. This work establishes a mechanistic foundation and design principle for GaN-based hybrid-dimensional optoelectronic synapses, extending their operating wavelength and enabling multi-band neuromorphic computing.

The rapid growth of artificial intelligence is intensifying demands for high-throughput, energy-efficient, and low-latency tensor processing. Photonic computing offers intrinsic bandwidth and parallelism, but it’s scaling often depends on adding optical channels or replicating physical processing elements. Here, we demonstrate reconfigurable silicon photonic computing through the tensorization of independently addressable wavelength, optical-mode, spatial, and temporal degrees of freedom. Wavelength, mode, and space serve as concurrent tensor axes, whereas temporal multiplexing applies successive weight sequences and convolution kernels to the same microring elements, thereby instantiating multiple effective logical nodes and reconfiguring the implemented operator. The proposed and fabricated circuit implements distinct fully connected and convolutional operations and supports single-node classification and convolution, four-directional edge extraction using nine microring modulators, and fingerprint recognition with a photonic-electronic Siamese network. At the single-node level, the system achieves a computing density of approximately 32.1 TOPS mm⁻² at 5-bit precision and an energy efficiency of approximately 2.3 fJ OP⁻¹. This work establishes a CMOS-compatible route from channel-level parallelism to dimension-aware tensor architectures whose logical capacity need not scale proportionally with physical device count.

Two-dimensional (2D) materials show great promise for building next-generation memristors. However, their application in self-rectifying memristors (SRMs)—crucial for suppressing sneak-path currents in high-density arrays—is still underexplored. In this work, we address this gap by developing ultrathin non-layered Co₃O₄ nanosheets through a vapor-phase growth strategy and precisely engineering their oxygen vacancies for high-performance SRMs. Our synergistic approach, combining salt-assisted vapor-liquid-solid, hydrate-assisted, and spatial confinement methods, enables the controlled synthesis of high-quality Co₃O₄ nanosheets as thin as 0.46 nm with a single-atomic-layer thickness. We demonstrate that magnetically driven rapid thermal annealing (MD-RTA) effectively increases the oxygen vacancy (O_v) concentration from 15.15% to 33.15%, as quantitatively confirmed by XPS, Raman, and KPFM. The resulting memristor exhibits excellent self-rectifying resistive switching behavior, with a high rectification ratio exceeding 10⁴ and a large ON/OFF ratio over 10⁴. The device also achieves high switching uniformity (coefficient of variation, C_v = 0.0979), stable cycling endurance over 100 DC cycles, and room-temperature operation. This study provides a reliable synthesis route for 2D non-layered materials and highlights defect engineering as an effective strategy for developing advanced in-memory computing devices with inherent crosstalk immunity.

The p-n diodes are crucial in electronics and optoelectronics. One approach to forming a p-n diode involves using a MoS₂/WSe₂ heterojunction. However, to achieve ohmic contact with the metal, MoS₂ and WSe₂ typically require different electrode materials. We present a strategy to fabricate MoS₂/WSe₂ heterojunction devices using a single metal nickel (Ni) as electrodes, with performance tuned solely by varying contact positions. When the electrodes contact both materials on either side, the device suppresses current flow in both directions. However, when one electrode contacts MoS₂ and the other contacts the heterojunction stack, the device yields pronounced rectification behavior, achieving a rectification ratio (RR) of 565, tunable via gate voltage. This enhancement arises as WSe₂ effectively acts as a base region, akin to that in bipolar junction transistors (BJTs), facilitating electron collection with minimal recombination. The device exhibits superlinear optical power dependence at zero bias, and has a fast response with a rise time of 67 μs and a fall time of 60 μs. Our approach offers valuable guidance for designing next-generation electronics.

Microring resonators (MRRs) are key building blocks in integrated photonics, but their performances usually suffer from limitations in extinction ratio and slope rate (SR), primarily due to their symmetrical Lorentzian resonance line shape. To overcome these limitations, special transmission spectra (STS), such as Fano resonance and electromagnetically induced transparency (EIT)-like resonance, offer asymmetric line shapes that exhibit a higher extinction ratio (ER) and a steeper SR, thereby enhancing the sensitivity and selectivity of optical switches, filters, and high-sensitivity sensors. However, the current reported works typically achieved only one type of STS and had limited tunability. In this Letter, we experimentally demonstrate a novel, to the best of our knowledge, device using two cascaded MRRs with different quality factors to generate Fano and EIT-like resonances at distinct ports. The ER can reach up to 31.2 dB with a sharp SR of 130.1 dB/ nm, for Fano resonance, and the EIT-like resonance is 12.4 dB. By adjusting the resonator wavelength of the MRRs and the phase shifter, the STS can be working at any desired wavelength. The device is demonstrated on a silicon-on-insulator platform, offering versatile application potential in optical sensors, slow and fast light generation, and microwave photonics.

The conventional theory of the bipolar junction transistor (BJT) does not clarify the electric field and its effect on the carrier transit in the uniformly doped base region, although the electric field is considered to be a second-order effect at high-level injection. In this study, analytical models of the carrier distribution, electric field, and carrier transit time in the base region are developed without making additional assumptions. It is found that the electric field may change direction, from forward to reverse, as long as the injection level reaches a criterion, affecting the carrier transport behavior. The models are based on the renovated p–n junction theory, provide insight into the carrier transit and are able to cover all levels of injection without the need to handle the low- and high-level injection separately. These models hold significance in retrieving the theoretical integrity of bipolar junction devices, and can be useful for further investigation in structure design, capacitance control, and AC performance optimization of the p–n junction-based device.

The built-in electric field at the heterojunction interface can effectively separate electron–hole pairs, which can effectively increase the photocurrent and suppress the dark current. The p–n junction can provide a good depletion layer, so p–n junction photodetectors based on two-dimensional materials are rapidly developing. In this study, Nb-doped MoS2 as a p-type semiconductor and n-type α-In2Se3 were used to form a van der Waals heterojunction photodetector. This photodetector achieves photodetection in the visible to near-infrared range with a responsivity (R) of 87 A/W and a specific detectivity (D*) of 7.5 × 1011 Jones. The carriers introduced by doping make the device less suppressive to dark currents, but maintain a high photoresponsivity. This study adopts doping modulation of the conductive properties for p–n junction photodetectors, and the results are expected to further enhance the photodetection performance.

The α-In₂Se₃ material is a two-dimensional ferroelectric semiconductor whose structural asymmetry gives it spontaneous polarization properties, and exhibits a direct bandgap structure when it is multilayered. α-In₂Se₃ is an n-type semiconductor, which is usually used in experiments to form heterojunctions with p-type semiconductors to prepare photodetectors. In this paper, we designed α-In₂Se₃/Nb-doped MoS₂ heterojunction, because Nb doping is a good p-type dopant for MoS₂. Our research shows that: the heterojunction exhibits type-Ⅱ band alignment; the band offset can be changed by the out-of-plane polarization direction; doping can modulate the Fermi energy level position of MoS₂ and thus further modulate the band alignment and band offset. The α-In₂Se₃/Nb-doped MoS₂ heterojunction is expected to be applied to the field of photodetectors, and we proposed a method to adjust the band alignment of the heterojunction by adjusting the doping concentrations.

For 2-D materials, carrier trapping by interfacial traps/impurities is an important approach for enhanced photoconductive gain and responsivity, however, it is accompanied by a long response time. Here, we demonstrate a suspended multilayer WSe $_{\text{2}}$ photodetector that balances responsivity and response speed. By using van der Waals (vdW) contacts, the suspended WSe $_{\text{2}}$ photodetector has been built, and the device shows a good response in visible wavelengths. The responsivity can be up to 30.44 A/W at 20 nW and $\textit{V}_{\text{GS}}$ $=$ $-$ 60 V, which is higher than the substrate-supported photodetector. The improvement comes mainly from the effective weakening of the Schottky barrier by vdW contact. Moreover, the response speed can be tuned by the interfacial coupling effect (ICE) caused by gate voltage. The suspended WSe $_{\text{2}}$ photodetector shows a rapid response of 0.23/0.1 s at $\textit{V}_{\text{GS}}$ $=$ 0 V, and the response time decreases to 30 ms at $\textit{V}_{\text{GS}}$ $=$ 20 V. The response speed remains at the same level as that of substrate-supported photodetector, owing to the reduction of SiO $_{\text{2}}$ interface traps.

Cathode shorts are an essential part in light-triggered thyristors (LTTs) that are utilized to achieve adequate dv/dt capability and switching characteristics. In this paper, we designed cathode shorts structures specifically for small-size LTTs; the patterns and structural parameters were shown. Devices were fabricated and measured, and the influences of the cathode shorts on device performance were examined. The results showed that, based on the optimized design, the cathode shorts allowed excellent dv/dt capability and switching performance while achieving good optoelectronic properties.