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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
摘要： We report promising results regarding the possible use of AlN or Al2O3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN ?lms are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al2O3 ?lms are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric ?eld across the AlN or Al2O3 is ～ 3 MV/cm or ～ 5 MV/cm respectively. By depositing an additional SiO2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al2O3 layers, it is possible to increase the breakdown voltage of the MIS capacitors signi?cantly without having pronounced impact on the quality of the AlN/SiC or Al2O3/SiC interfaces.
关键词： MIS structure,Interface traps,Al2O3/4H-SiC interface,AlN/4H-SiC interface
更新于2025-11-14 17:28:48
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AlN-based hybrid thin films with self-assembled plasmonic Au and Ag nanoinclusions
摘要： Aluminum nitride (AlN)-based two-phase nanocomposite thin films with plasmonic Au and Ag nanoinclusions have been demonstrated using a one-step thin film growth method. Such AlN-based nanocomposites, while maintaining their wide bandgap semiconductor behavior, present tunable optical properties such as bandgap, plasmonic resonance, and complex dielectric function. Depending on the growth atmosphere, the metallic nanoinclusions self-organized into different geometries, such as nano-dendrites, nano-disks, and nanoparticles, providing enhanced optical anisotropy in-plane and out-of-plane. The infrared transmission measurements demonstrate the signature peaks of AlN as well as a broad transmission window attributed to the plasmonic nanoinclusions. This unique AlN-metal hybrid thin film platform provides a route to modulate the optical response of wide bandgap III-V nitride semiconductors towards infrared sensing or all optical based integrated circuits.
关键词： plasmonic Au and Ag nanoinclusions,infrared sensing,integrated circuits,AlN-based hybrid thin films,optical properties
更新于2025-10-22 19:40:53
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Single-Crystal ZnO/AlN Core/Shell Nanowires for Ultraviolet Emission and Dual-Color Ultraviolet Photodetection
摘要： Core–shell nanostructures can combine the advantages of different functional materials to realize property tunability and enhance optical and optoelectrical performance. Here, vertically aligned ZnO/AlN core/shell nanowires have been facilely fabricated by sputtering AlN layer onto the ZnO nanowires grown by vapor phase transport. The morphological and structural characterization reveals that single-crystal AlN shell layer with thickness of ≈15 nm is coated uniformly on the single-crystal ZnO nanowire with diameters of ≈330 nm. The core/shell nanowire exhibits 24 times enhancement of ultraviolet emission and quenching of the deep level emission from ZnO. Moreover, under ultraviolet irradiation (325 nm), the photodetector based on the core/shell nanowire displays higher photoresponsivity (from 3.8 × 103 to 2.05 × 104 A W?1), faster response speed (from 397 to 28 ms), and higher I325nm/Idark ratio (from 453 to 1.1 × 104) than that bare ZnO nanowire device. Under the vacuum ultraviolet (193 nm) illumination, the I193nm/Idark ratio and photoresponsivity are 300 and 381 A W?1, respectively. In one word, this paper employs a facile and general technique to solve a challenging fabrication issue, and obtains perfect crystal core/shell structure with high performance for ultraviolet emission and detection.
关键词： single-crystal core/shell,AlN,ZnO nanowires,ultraviolet emission,dual-color ultraviolet photodetection
更新于2025-09-23 15:23:52
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Improvement of the critical temperature of NbTiN films on III-nitride substrates
摘要： In this paper, we study the impact of using III-nitride semiconductors (GaN, AlN) as substrates for ultrathin (11 nm) superconducting films of NbTiN deposited by reactive magnetron sputtering. The resulting NbTiN layers are (111)-oriented, fully relaxed, and they keep an epitaxial relation with the substrate. The higher critical superconducting temperature (Tc = 11.8 K) was obtained on AlN-on-sapphire, which was the substrate with smaller lattice mismatch with NbTiN. We attribute this improvement to a reduction of the NbTiN roughness, which appears associated to the relaxation of the lattice misfit with the substrate. On AlN-on-sapphire, superconducting nanowire single photon detectors (SNSPDs) were fabricated and tested, obtaining external quantum efficiencies that are in excellent agreement with theoretical calculations.
关键词： single photon detector,superconductor,NbTiN,AlN,GaN
更新于2025-09-23 15:23:52
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Growth of high quality AlN/sapphire templates with high growth rate using a medium-temperature layer
摘要： In this work, crack-free 3.3-μm-thick AlN ?lms with high crystalline quality and atomic smooth surfaces were achieved on sapphire substrates at a high growth rate of 2.9 μm/h. Double-axis x-ray rocking curves showed a full width at half maximum of 315 and 419 arc sec for (0002) and (101ˉ2) re?ections, respectively, corresponding to a total threading dislocation (TD) density of 9.79 × 10^8 cm^-2. Cracks were suppressed and crystalline quality was improved by introducing a medium-temperature (MT) layer. It was found that the density of both screw- and edge-type TDs could be signi?cantly reduced by introducing the MT-AlN layer under appropriate temperature. The crystalline improvement is attributed to the delayed coalescence of the AlN islands and higher probability for the annihilations of TDs by the MT-AlN layer under appropriate temperature. This method provides a promising way in growing practical thick AlN templates suitable for large-scale industrial production.
关键词： High growth rate,MOCVD,Crack-free,Medium-temperature layer,AlN
更新于2025-09-23 15:22:29
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Electrical properties of 4H-SiC MIS capacitors with AlN gate dielectric grown by MOCVD
摘要： We report on the electrical properties of the AlN/4H-SiC interface using capacitance- and conductance-voltage (CV and GV) analysis of AlN/SiC MIS capacitors. The crystalline AlN layers are made by hot wall MOCVD. CV analysis at room temperature reveals an order of magnitude lower density of interface traps at the AlN/SiC interface than at nitrided SiO2/SiC interfaces. Electron trapping in bulk traps within the AlN is significant when the MIS capacitors are biased into accumulation resulting in a large flatband voltage shift towards higher gate voltage. This process is reversible and the electrons are fully released from the AlN layer if depletion bias is applied at elevated temperatures. Current-voltage (IV) analysis reveals that the breakdown electric field intensity across the AlN dielectric is 3–4 MV/cm and is limited by trap assisted leakage. By depositing an additional SiO2 layer on top of the AlN layer, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having much impact on the quality of the AlN/SiC interface.
关键词： AlN/4H-SiC interface,MIS capacitors,Gate dielectrics
更新于2025-09-23 15:22:29
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823 mA/mm drain current density and 945 MW/cm2 Baliga’s figure of merit enhancement-mode GaN MISFETs with a novel PEALD-AlN/LPCVD-Si3N4 dual gate dielectric
摘要： In this letter, we demonstrate a novel PEALD-AlN/LPCVD-Si3N4 dual gate dielectric employed in enhancement-mode GaN MISFETs, where the gate recess is fabricated based on our proposed self-terminating gate recess etching technique using GaN cap layer as recess mask. By using LPCVD-Si3N4 and PEALD-AlN dual gate dielectric layer, the devices exhibit a high quality gate dielectric and a good GaN channel interface, yielding a high gate swing up to 18V and a high channel effective mobility of 137 cm2/V?s at such high gate bias. Thus, the fabricated devices feature a high maximum drain current density of 823 mA/mm, a threshold voltage of 2.6 V, an on-resistance of 7.4 Ω?mm, and an ON/OFF current ratio of 108 with gate-drain distance of 2 μm. Meanwhile, a high OFF-state breakdown voltage of 1290 V is achieved with 10 μm gate-drain distance. The corresponding specific on-resistance is as low as 1.76 mΩ?cm2, leading to a high Baliga’s ?gure of merit of 945 MW/cm2.
关键词： self-terminating etching,enhancement-mode GaN MISFETs,plasma-enhanced atomic layer deposition (PEALD) AlN,LPCVD Si3N4
更新于2025-09-23 15:21:21
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Advances in GaN Crystals and Their Applications
摘要： This special issue looks at the potential applications of GaN-based crystals in both ?elds of nano-electronics and optoelectronics. The contents will focus on the fabrication and characterization of GaN-based thin ?lms and nanostructures. It consists of six papers, indicating the current developments in GaN-related technology for high-ef?ciency sustainable electronic and optoelectronic devices, which include the role of the AlN layer in high-quality AlGaN/GaN heterostructures for advanced high-mobility electronic applications and simulation of GaN-based nanorod high-ef?ciency light-emitting diodes for optoelectronic applications. From the results, one can learn the information and experience available in the advanced fabrication of nanostructured GaN-based crystals for nano-electronic and optoelectronic devices.
关键词： MOSFET,AlN,InN,InGaN,AlGaN,LED,GaN
更新于2025-09-23 15:21:21
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Graphene-assisted molecular beam epitaxy of AlN for AlGaN deep-ultraviolet light-emitting diodes
摘要： We report on the van der Waals epitaxy of high-quality single-crystalline AlN and the demonstration of AlGaN tunnel junction deep-ultraviolet light-emitting diodes directly on graphene, which were achieved by using plasma-assisted molecular beam epitaxy. It is observed that the substrate/template beneath graphene plays a critical role in governing the initial AlN nucleation. In situ reflection high energy electron diffraction and detailed scanning transmission electron microscopy studies confirm the epitaxial registry of the AlN epilayer with the underlying template. Detailed studies further suggest that the large-scale parallel epitaxial relationship for the AlN epilayer grown on graphene with the underlying template is driven by the strong surface electrostatic potential of AlN. The realization of high-quality AlN by van der Waals epitaxy is further confirmed through the demonstration of AlGaN deep-ultraviolet light-emitting diodes operating at 260 nm, which exhibit a maximum external quantum efficiency of 4% for an unpackaged device. This work provides a viable path for the van der Waals epitaxy of ultra-wide bandgap semiconductors, providing a path to achieve high performance deep-ultraviolet photonic and optoelectronic devices that were previously difficult.
关键词： AlGaN,AlN,molecular beam epitaxy,deep-ultraviolet,light-emitting diodes,van der Waals epitaxy
更新于2025-09-23 15:21:01
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Molecular beam homoepitaxy on bulk AlN enabled by aluminum-assisted surface cleaning
摘要： We compare the effectiveness of in situ thermal cleaning with that of Al-assisted cleaning of native surface oxides of bulk AlN for homoepitaxial growth by molecular beam epitaxy. Thermal deoxidation performed at 1450 (cid:2)C in vacuum results in voids in the AlN substrate. On the other hand, Al-assisted deoxidation at (cid:3)900(cid:2)C results in high-quality AlN homoepitaxy, evidenced by clean and wide atomic terraces on the surface and no extended defects at the growth interface. This study shows that Al-assisted in situ deoxidation is effective in removing native oxides on AlN, providing a clean surface to enable homoepitaxial growth of AlN and its heterostructures; furthermore, it is more attractive over thermal deoxidation, which needs to be conducted at much higher temperatures due to the strong bonding strength of native oxides on AlN.
关键词： surface cleaning,homoepitaxy,molecular beam epitaxy,aluminum-assisted cleaning,AlN
更新于2025-09-23 15:21:01