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[Lecture Notes in Electrical Engineering] Engineering Vibration, Communication and Information Processing Volume 478 (ICoEVCI 2018, India) || Optimization of AlGaN QW Heterostructure for UV Applications
摘要： This paper reports the existence of ultraviolet (UV) optical gain in AlN/AlGaN/AlN nanoscale heterostructure consisting of 50 nm quantum well (QW) of AlGaN material sandwiched between layers of AlN material. The designed heterostructure is of type-I and assumed to be grown on GaN substrate. The optical gain of the heterostructure has been optimized utilizing k.p method. The simulation result shows that the peak optical gain in the AlGaN QW heterostructure lies at ~2400 ? (UV region) of the order of ~760 cm, which proves the potentiality of the AlN/AlGaN/AlN heterostructure as a source of UV radiations.
关键词： Type-I heterostructure,AlN,Optical gain,AlGaN
更新于2025-09-23 15:21:01
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Reference Module in Materials Science and Materials Engineering || Organometallic Vapor Phase Epitaxial Growth of Group III Nitrides ☆
摘要： The III-nitrides of aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN) and their solid solutions form most commonly in the low-temperature wurtzite crystal structure shown in Fig. 1(a). Overall, this structure possesses a hexagonal unit cell with lattice constants c (o00014 axes) and a (o11204 axes). The atomic arrangement within this structure consists of two interpenetrating, closest packed metal and nitrogen lattices in which each atom of one type is bonded to four atoms of the other to form AB4 tetrahedra. The space group is P63mc.
关键词： GaN,OMVPE,Organometallic Vapor Phase Epitaxy,Group III Nitrides,Polarization,Dislocations,InN,Buffer Layers,AlN,Substrates
更新于2025-09-23 15:21:01
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Reducing stimulated emission threshold power density of AlGaN/AlN multiple quantum wells by nano-trench-patterned AlN template
摘要： We investigate the crystal quality of epitaxy lateral overgrowth (ELOG) AlN layers and the performance of optical pumping AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs) on two different patterned AlN templates upon sapphire substrate. The full width at half maximum values of (0002) and (10 1(cid:2)2) X-ray diffraction rocking curves of the ELOG AlN layer on the nano-net-patterned AlN template are 76 and 306 arcsec, and the values of that on the nano-trench-patterned AlN template are 114 and 357 arcsec, respectively. Nevertheless, the threshold power density (Pth) of the 272-nm lasing from the multiple quantum wells (MQWs) on the nano-trench-patterned AlN template is 11% lower than that on the nano-net-patterned AlN template. The reason is that the continuous low threading dislocation density (TDD) MQWs zones above the ELOG coalescent areas upon trenched patterns are in parallel with the stimulated light emission direction. When light resonates through the continuous low TDD MQWs zones, it has higher optical gain and less non-radiative recombination than the case on the nano-net-patterned AlN template where the low TDD MQWs zones are discontinuous on the light path. The results indicate that not only the crystal quality but also the TDD distribution originated from the ELOG on the patterned templates have crucial influence on the Pth, and trench-patterned template can improve the performance of waveguide LDs with Fabry-Perot cavities.
关键词： laser diode,deep ultraviolet,multiple quantum wells,AlGaN,AlN
更新于2025-09-23 15:21:01
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai, China (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Batch-Mode μUSM Process for Surrounding Air Cavity and TCV Holes of AlN Ceramic Substrate Application for Patch Antenna
摘要： Narrow bandwidth of miniaturization patch antenna caused by substrate material severely limits its applications, fabricating air cavity on AlN ceramic substrate for decreasing its dielectric constant is a potential method for increasing the bandwidth. But it’s a critical challenge for simultaneous fabricating of surrounding air cavity and TCV holes on AlN ceramic substrate with high precision. This paper presents a patch antenna on AlN ceramic substrate with surrounding air cavity and TCV holes. And its key process of surrounding air cavity and TCV holes fabrication on AlN ceramic is developed by batch-mode μUSM. AlN ceramic simple with step depth of surrounding air cavity and TCV blind hole is machined simultaneously. Its machining feature resolution and surface roughness are below 1μm and Ra 200nm respectively, machining removal rate is higher than 4.5μm/min. The patch antenna property is simulated and analyzed, the results show the increment of bandwidth reach up to 68.42% because of the surrounding air cavity existing.
关键词： AlN ceramic,simultaneous machining,patch antenna,surrounding air cavity and TCV holes,batch-mode μUSM
更新于2025-09-23 15:21:01
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Fabrication of AlN/GaN MSM photodetector with platinum as schottky contacts
摘要： The epitaxial aluminium nitride (AlN) layer was fabricated on a silicon (111) substrate by solid phase radio frequency (RF) MBE The samples morphological characteristic was successfully studied by ?eld emission SEM. Low photo-response of the hetero-structure layers is one of the main obstacles in order to fabricate a high performance of photodetector device. The platinum contacts on AlN/GaN metal-semiconductor-metal (MSM) photodetector were formed by RF sputtering machine. The conductivity behaviours, Schottky barrier height (SBH), photo-responses of the device were examined by source meter measurement. The SBH values of photo-device sensing were calculated as 0.488 eV and 0.479 eV for dark current and photo current, respectively. Good response times of the device were recorded as 21.48 ms and 12.69 ms for the bias voltage of 1 volt.
关键词： AlN,photodetector,aluminum nitride
更新于2025-09-23 15:19:57
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Suppression of dislocation-induced spiral hillocks in MOVPE-grown AlGaN on face-to-face annealed sputter-deposited AlN template
摘要： AlGaN films were grown on face-to-face annealed sputter-deposited AlN/sapphire (FFA Sp-AlN) templates via metalorganic vapor phase epitaxy (MOVPE), and the growth behavior of the AlGaN films was investigated. The sapphire substrates with small off-cut exhibited poor surface flatness of AlGaN grown on the FFA Sp-AlN templates owing to the formation of large hillock structures. To understand the origin of these hillock structures, the crystallinity and surface morphology of conventional fully MOVPE-grown AlN/sapphire (MOVPE-AlN) templates and the FFA Sp-AlN template were comprehensively studied. The screw- and mixed-type threading dislocation density of the FFA Sp-AlN template was estimated to be approximately 1.8 × 106 cm?2, which was two orders of magnitude lower than that of the MOVPE-AlN template. Consequently, the uniquely observed growth of the hillock structures in the FFA Sp-AlN templates was attributed to their low density of screw- and mixed-type threading dislocations. The large surface off-cut sapphire substrates suppressed the hillock structures on the FFA Sp-AlN templates. The improvement in surface flatness resulted in better optical properties of multiple quantum wells grown on the AlGaN layer. These results demonstrate a promising method for achieving highly efficient and cost effective AlGaN based deep ultraviolet light-emitting diodes.
关键词： AlGaN,MOVPE,deep ultraviolet light-emitting diodes,hillock structures,FFA Sp-AlN
更新于2025-09-23 15:19:57
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Recovery kinetics in high temperature annealed AlN heteroepitaxial films
摘要： Based on the experimental dislocation annihilation rates, vacancy core diffusion-controlled dislocation climb was found as a dominant recovery mechanism in high temperature annealing of AlN heteroepitaxial films. Dislocation annihilation mechanisms via dislocation glide (with or without kinks) and vacancy bulk diffusion were found to be less significant. Cross-slip was also ruled out as a possible mechanism as a majority of dislocations in heteroepitaxial AlN films are threading edge dislocations. While dislocation climb through both vacancy bulk and core diffusion could offer a plausible explanation of the recovery process, the activation energy for the vacancy core diffusion-controlled dislocation climb was relatively low (4.3 ± 0.1 eV), as estimated from an Arrhenius plot. The validity of the vacancy core diffusion mechanism was also supported by a large vacancy mean free path (～240 nm), which was comparable to the sample thickness and thus the average dislocation length. Finally, the experimentally observed dislocation density reduction as a function of the annealing temperature and time was in good agreement with the vacancy core diffusion mechanism.
关键词： dislocation annihilation,high temperature annealing,AlN heteroepitaxial films,recovery kinetics,vacancy core diffusion
更新于2025-09-23 15:19:57
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Defect mediated transport in self-powered, broadband and ultrafast photoresponse of MoS <sub/>2</sub> /AlN/Si based photodetector
摘要： By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here we report a self-powered and ultrafast photodetector based on hybrid MoS2/AlN/Si heterostructure. The heterojunction is formed by depositing MoS2 thin film by pulsed laser deposition on AlN/Si(111) template. The vertical transport properties of the device under dark and light illumination conditions, exhibit an excellent photoresponse in a broad range of wavelengths (300–1100 nm) at 0 V. The maximum responsivity of this photodetector is found to be 9.93 A/W at wavelength of 900 nm. The device shows an ultrafast temporal response with response/recovery times of 12.5/14.9 μs. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy reveal presence of native oxygen impurities in AlN, throughout the bulk of the film. These oxygen defects form a deep donor level in AlN and play a crucial role in the transport of the photogenerated carriers, resulting in enhanced device performance.
关键词： broadband and ultrafast photoresponse,deep defects,MoS2,AlN,pulsed laser deposition
更新于2025-09-23 15:19:57
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Integral monolayer-scale featured digital-alloyed AlN/GaN superlattices using hierarchical growth units
摘要： Acquiring AlN/GaN digital alloys with matching coherent lattices, atomically sharp interfaces, and negligible compositional fluctuations remains a challenge. In this work, the nature and formation mechanism of the constituent elements of AlN and GaN atomic layers growth was examined by first-principle calculations and experimental demonstration. Basing on the calculated formation enthalpies, we developed a hierarchical growth method wherein AlN and GaN growth units are digitally stacked layer by layer through metal organic vapor-phase epitaxy, which involves the growth sequence instantaneously to control chemical potentials of the hierarchical growth units under different atmospheres. High-resolution X-ray diffraction and transmission electron microscopy confirmed that the hierarchical GaN and AlN growth units of digital-alloyed AlN/GaN structures had coherent lattices, abrupt interfaces, and integral monolayers at the atomic scale. The cathodoluminescence properties featured with single emission, combining with theoretical results, demonstrated that the capability of electronic energies via the digital-alloyed AlN/GaN superlattices. These results provide a basis toward the realization of other digital-alloyed nitride semiconductors.
关键词： digital-alloyed AlN/GaN superlattices,integral monolayer-scale,hierarchical growth units
更新于2025-09-19 17:15:36
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Microstructure and properties of TiAlN/AlN multilayers with different modulation periods
摘要： The effects of thicknesses of AlN layer on microstructures and properties of TiAlN/AlN multilayers were studied. TiAlN/AlN multilayers had been deposited on 304 stainless steels by magnetron sputtering system. The microstructure and properties of the multilayers were characterized by X-ray diffraction, vicker hardness tester, atomic force microscopy, and friction abrasion tester. The results show that under “template effect” of TiAlN layer, AlN layer is changed into face-centered cubic and grow epitaxially with TiAlN layer. The superhardness effect could be generated in the region with sharp interface. With the thickness of AlN layer in TiAlN/AlN multilayers, the properties of multilayer are firstly increase and then decrease. When the AlN layer thickness is 3.2nm, the multilayer has excellent properties. The hardness of multilayer is 30.98GPa, the roughness of multilayer is 20.2nm, and the coefficient of friction of multilayer is 0.61.
关键词： Tribological property,Hardness,Modulation period,TiAlN/AlN
更新于2025-09-19 17:15:36