With the increasing demand for low-resistivity substrates, growing heavily doped 4H-SiC crystals is emerging as a critical practice. Now, we report the growth of heavily nitrogen-doped, nitrogen-aluminum (N-Al) co-doped and nitrogen-gallium (N-Ga) co-doped 4H-SiC crystals by using the physical vapor transport (PVT) method. Comparative study shows that co-doping contributes to enhanced nitrogen incorporation efficiency and leads to lower resistivity. In addition, it is found that the heavy doping shifts the Fermi level of 4H-SiC into the conduction band. The temperature dependence of the mobility of heavily co-doped 4H-SiC indicates a thermally activated transport for electrons at temperatures above 300 K. Ga and Al atoms are found to effectively impede the glide and multiplication of basal plane dislocations (BPDs), reducing the density of BPDs. The N-Ga co-doping effectively suppresses the formation of stacking faults.
In this work, we demonstrate an Al-rich AlGaN channel metal insulator semiconductor HEMT device operating at >2 kV on a sapphire substrate. Devices with 2and 2.6 kV breakdown voltage demonstrated a Baliga figure of merit (BFOM) of 288 and 325 MW/cm(2) with an on-resistance of 14.15 and 21.02 m Omega.cm(2), respectively. Reported BFOM of 325 MW/cm(2) value is 1.7 times the state-of-the-art passivated AlGaN channel transistors on sapphire substrate. The obtained results represent the potential of the ultra-wide bandgap (UWBG) AlGaN channel transistors for advanced power electronics applications.
Lattice and microstructural phases are always critical for controlling optical, electronic, and optoelectronic characterizations of semiconductor materials and their functional devices. Gallium oxide (Ga2O3) is widely recognized as a promising material for solar-blind ultraviolet photodetectors, with both amorphous and crystalline phases offering distinct advantages. Nevertheless, inherent crystallinity issues still hinder device performance and practical application. In this work, we systematically investigated the correlation between microstructure and dynamic evolution of photogenerated carriers in Ga2O3 via crystal phase manipulation. High-performance nanocrystalline Ga2O3 photodetectors were demonstrated with a high detectivity of 3.50 & times; 1013 Jones and a larger photo-to-dark current ratio up to 5.56 & times; 104. Related photoresponsivity and rejection ratio of the ultraviolet photodetectors were significantly modulated by amorphous, nanocrystalline, and multicrystalline microstructural phases. This modulation is attributed to oxygen-vacancy-related defects, which introduce additional energy levels acting as electron donors that significantly alter the carrier concentration and thus regulate the signal intensity of the photoresponse. These insights underscore the critical role of structural phase engineering in Ga2O3 and provide valuable guidance for the design and optimization of high-performance solar-blind ultraviolet photodetectors.
Fluorescent antennas (FAs) based on quantum dots (QDs) are promising light-converting structures for optical wireless communication (OWC) owing to their high photoluminescence efficiency and ultrawide field of view (FOV). However, their stability is limited by degradation from water and oxygen, hindering long-term operation. Here, we present a strategy that combines a cross-linked resin with digital light processing (DLP) 3D printing to fabricate structurally programmable and environmentally robust FAs. The approach enables uniform QDs dispersion, high-resolution geometries, and tunable device architectures beyond conventional mold-based methods. Guided by Monte Carlo simulations, we further developed an encapsulated fluorescent antenna (EFA), in which the emissive QDs layer is fully enclosed in a transparent resin shell. This design provides effective isolation from moisture and oxygen while functioning as a low-loss optical waveguide. The optimized EFA achieved a side-emission efficiency of 10.9% and a wide FOV of 150 degrees. Importantly, the EFA retained over 70% of its emission intensity after 10 days in water. In the communication tests, the EFA demonstrated a 26 MHz modulation bandwidth and a 135 Mbps data rate. These results establish DLP-printed EFA as a versatile and stable platform for next-generation underwater photonic communication devices.
Li-S batteries possess an ultrahigh theoretical specific capacity of 1675 mAh g-1, yet their practical application is still hindered by the shuttle effect and sluggish sulfur redox kinetics. Current research on Li-S batteries mainly focuses on interface engineering strategies, while a systematic understanding of how the built-in electric field (BIEF) induced by work function mismatch regulates interfacial charge redistribution and sulfur-species conversion remains limited. In this work, we constructed a Co@NC Mott-Schottky heterojunction to induce interfacial charge redistribution. Experimental and theoretical results demonstrate that work function mismatch between the two phases also drives the spontaneous formation of a BIEF, which accelerates the bidirectional redox kinetics of sulfur. This BIEF drives the directional migration of interfacial charges and modulates the energy barriers of sulfur species conversion. Consequently, the Co@NC/S cathode delivers a high capacity retention of 82.1% after 400 cycles at 5 C, and retains 77.2% after 120 cycles under high sulfur loading (5.6 mg cm-2) and lean electrolyte conditions (E/S = 4.0 mu L mg-1). This work reveals the critical role of BIEF in boosting sulfur electrochemistry and provides a transferable interface engineering design strategy for high-performance Li-S batteries.
