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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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Extremely Low Dark Current and Detection Range Extension of Ga2O3 UV Photodetector using Sn Alloyed Nanostructures
摘要： A unique metal-semiconductor-metal (MSM) photodetector has been fabricated using Sn incorporation in Ga2O3 forming SnxGa1-xO nanostructures (Ns) with platinum (Pt) metal as contacts. The mixed nanostructures (MNs) has been attributed to an increment in the detection range of UV (254 – 302 nm) with ultra-low dark current, hence a potential device in the field of long range deep-UV detector. SnxGa1-xO (Ns) are deposited on c-plane sapphire using low-pressure chemical vapour deposition (LPCVD). From the X-ray diffraction results, existence both SnxGa1-xO and tetragonal SnO2 MNs are confirmed. The XRD peak shifts in SnxGa1-xO is attributed to the integration of Sn with Ga forming SnxGa1-xO alloy with x to be ~7.3% determined from the Vegard’s law. The FESEM images show the thick diameter wire-shaped nanostructures. The absorption spectra show a trace of two absorption edges corresponding to both SnxGa1-xO and SnO2 Ns. Photo to dark current ratio (PDCR) of the fabricated photodetector is large (103) at 2 V bias with fast fall time of 0.18 s. The detector reveals self-powered behaviour also with PDCR > 104 at 0 V bias. The dark current is ultra-low (13 pA at 5 V) due to high barrier height of Pt and the UV detection range has been extended from 254 – 302 nm with a very small drop in PDCR owing to incorporation of Sn.
关键词： LPCVD,Nanostructures,Photodetector,Gallium Oxide
更新于2025-09-23 15:21:01
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Influence of boron doping amount on properties of ZnO:B films grown by LPCVD technique and its correlation to a-Si:H/??c-Si:H tandem solar cells
摘要： Boron-doped ZnO:B (BZO) films with various doping levels have been prepared on large-area substrates by low pressured chemical vapor deposition technique. The influence of doping amount on electrical and optical properties of BZO films has been investigated. It is found that ZnO phase synthesis is hardly affected when the doping gas flow varies from 25 to 100 sccm, but the preferential orientation of grain growth is influenced progressively. It is interesting that there should be a threshold value of doping gas flow of 75 sccm that will cause an abrupt reduction in grain size of BZO and therefore dramatically weakens the light-scattering capacity of the film. It is also noted that the boron atoms doped in BZO films are partly electrically active, and moreover, the heavier doping level, the more inactive B atoms, which not only reduces carrier mobility, but also boosts a stronger light absorption due to enhanced impurity scattering. When the doping gas flow is 75 sccm, the BZO film can achieve a proper comprehensive property with a Rsq of 15.2 Ω/□, an average haze of 21.3% and an average TT of 80.2%. Using this film as the front electrode of a-Si:H/μc-Si:H solar cell, the optimum performance of the solar cell with a Jsc of 12.68 mA/cm2, a Voc of 1.385 mV, and an initial efficiency (η) of 11.83% was obtained.
关键词： a-Si:H/μc-Si:H tandem solar cells,Boron-doped ZnO:B films,doping amount,LPCVD technique,electrical and optical properties
更新于2025-09-23 15:21:01
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The impacts of LPCVD wrap-around on the performance of n-type tunnel oxide passivated contact c-Si solar cell
摘要： In this paper, Tunnel Oxide Passivated Contact (TOPCon) silicon solar cells with the industrial area (244.32cm2) are fabricated on N-type silicon substrates. Both the ultra-thin tunnel oxide layer and phosphorus doped polycrystalline silicon (polysilicon) thin film are prepared by the LPCVD system. The wrap-around of polysilicon is observed on the surface of borosilicate glass (BSG). The polysilicon wrap-around can form a leakage current path, thus degrades the shunt resistance of solar cells, and leads to the degradation of solar cell efficiency. Different methods are adopted to treat the polysilicon wrap-around and improve shunt resistance of solar cells. The experimental results indicate that a chemical etching method can effectively solve the problem of polysilicon wrap-around and improve the performance of solar cells. Finally, a conversion efficiency of 22.81% has been achieved by our bifacial TOPCon solar cells, with Voc of 702.6 mV, Jsc of 39.78 mA/cm2 and FF of 81.62 %.
关键词： LPCVD,wrap-around,Tunnel oxide passivated contact,polycrystalline silicon thin film
更新于2025-09-23 15:21:01
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Interface charge engineering in down-scaled AlGaN (<6a??nm)/GaN heterostructure for fabrication of GaN-based power HEMTs and MIS-HEMTs
摘要： The physical mechanism for recovery of 2D electron gas (2DEG) in down-scaled AlGaN/GaN heterostructures with SiNx layers grown by low-pressure chemical vapor deposition (LPCVD) was investigated by means of Hall-effect characterization, scanning Kelvin probe microscopy (SKPM), and self-consistent Poisson–Schr€odinger calculations. Observations using SKPM show that the surface potential of the AlGaN/GaN heterostructure remained nearly unchanged ((cid:2)1.08 eV) as the thickness of the AlGaN barrier was reduced from 18.5 to 5.5 nm and likely originated from the surface pinning effect. This led to a signi?cant depletion of 2DEG from 9.60 (cid:3) 1012 to 1.53 (cid:3) 1012 cm(cid:4)2, as determined by Hall measurements, toward a normally OFF 2DEG channel. Based on a consistent solution of the Schr€odinger–Poisson equations and analytical simulations, approximately 3.50 (cid:3) 1013 cm(cid:4)2 of positive ?xed charges were con?rmed to be induced by a 20-nm LPCVD-SiNx passivation over the AlGaN/GaN heterostructures. The interface charge exerted a strong modulation of band bending in the down-scaled AlGaN/GaN heterostructure, contributing to the ef?cient recovery of 2DEG charge density ((cid:2)1.63 (cid:3) 1013 cm(cid:4)2). E-mode ultrathin-barrier AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors with a low ON-resistance (RON), high ON/OFF current ratio, and steep subthreshold slope were implemented using LPCVD-SiNx passivation.
关键词： AlGaN/GaN heterostructure,power HEMTs,LPCVD-SiNx passivation,2D electron gas,MIS-HEMTs,interface charge engineering
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Ultra-thin LPCVD SiN <sub/>x</sub> /n+poly-Si passivated contacts a?? A possibility?
摘要： This work explores the possibility of using ultrathin silicon nitride (SiNx) films with high positive fixed charge in a SiNx/poly-Si passivating contact. The factors including (i) film thickness, (ii) annealing condition (time, temp and ambient) and (iii) surface pre-treatment were optimized to boost the passivation performance of ultrathin LPCVD SiNx films. Our preliminary experiments reveal excellent surface passivation and low recombination current density, Jo (45 fA.cm-2) by ~1.5 nm thick LPCVD SiNx films when subjected to an air ambient anneal at 800?C for 30 mins. This is due to the formation of high positive fixed charge density (1.5 ?10 12 cm-2). Air ambient annealed (465 μs) samples also have a higher lifetime when compared to the forming gas annealed (208 μs) samples. These passivating SiNx films were further integrated into SiNx/n+poly-Si contacts and characterized for Jo,contact and tunneling resistance, ?contact. The best SiNx/n+poly-Si passivated contact in this study has Jo, contact = 5.9 fA.cm-2, ?contact = 0.525 Ω.cm2 and an efficiency potential > 22.75%. According to our knowledge, it is the first report confirming the formation of passivated contacts with SiNx as the dielectric tunnel layer.
关键词： poly-Si,TEM,LPCVD SiNx,annealing,lifetime studies,passivated contact,silicon nitride,tunnel layer
更新于2025-09-23 15:19:57
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Optimum reproduction and characterization of graphene on copper foils by low pressure chemical vapor deposition
摘要： Although the chemical vapor deposition synthesis of scalable graphene was done by many different groups, growing mechanism and optimization of graphene on copper foils has not yet been fully understood under appropriate conditions. In the context of low pressure chemical vapor deposition, annealing of copper can lead to very large and flat grains for uniform formation of monolayer graphene on copper via a combination of H2 and CH4 gases at a substrate temperature of 1000°C. Growing tendency of graphene domains was investigated according to different exposure time and flux of CH4. Graphene was found not to be a uniform coverage of the whole copper surface due to inhomogeneous surface roughness among different copper grains. However, it can be improved more significantly by annealing copper up to near its melting temperature before graphene formation at lower substrate temperature of 1000°C. For this reason, we found that the thermal resistance of our materials acts as a function of the degree of graphene coverage on copper. Our graphene on copper foils was investigated by optical microscopy, Raman spectroscopy, scanning electron microscopy and heat transfer technique.
关键词： Thermal resistance,Interface,Copper foils,LPCVD graphene,Graphene on copper
更新于2025-09-23 15:19:57
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Thickness-tunable growth of ultra-large, continuous and high-dielectric h-BN thin films
摘要： The outstanding thermal properties, mechanical properties and large optical bandgap of hexagonal boron nitride (h-BN) make it very attractive for various applications in ultrathin 2D microelectronics. However, the synthesis of large lateral size and uniform h-BN thin films with a high breakdown strength still remains a great challenge. Here, we comprehensively investigated the effect of growth conditions on the thickness of h-BN films via low pressure chemical vapor deposition (LPCVD). By optimizing the LPCVD growth parameters with electropolished Cu foils as the deposition substrates and developing customized "enclosure" quartz-boat reactors, we achieved thickness-tunable (1.50–10.30 nm) growth of h-BN thin films with a smooth surface (RMS roughness is 0.26 nm) and an ultra-large area (1.0 cm × 1.0 cm), meanwhile, the as-grown h-BN films exhibited an ultra-high breakdown strength of ~10.0 MV cm?1, which is highly promising for the development of electrically reliable 2D microelectronic devices with an ultrathin feature.
关键词： dielectric breakdown strength,h-BN,thin films,LPCVD,2D microelectronics,hexagonal boron nitride
更新于2025-09-19 17:15:36
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Hydrogen effects on AlGaN/GaN MISFET with LPCVD-SiNx gate dielectric
摘要： In this work, the effects of hydrogen on AlGaN/GaN MISFET with SiNx gate dielectric were investigated. It is found that after the hydrogen exposure, (1) the AlGaN/GaN MISFET exhibits better DC performance with larger maximum transconductance, (2) the gate lag phenomenon is effectively suppressed and (3) the 1/f noise performance is improved with lower noise magnitude. These results are different from the previous observations in other III-V semiconductor devices. Based on the theoretical analysis by space charge limited current (SCLC) and low-frequency noise (LFN) models, we propose that the hydrogen treatment induces hydrogen incorporation into SiNx, which could passivate the defect centers. These findings demonstrate the high hydrogen tolerance of AlGaN/GaN MISFET.
关键词： LPCVD-SiNx,hydrogen effect,AlGaN/GaN MISFET
更新于2025-09-19 17:15:36
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Enhanced gate stack stability in GaN transistors with gate dielectric of bilayer SiN <sub/>x</sub> by low pressure chemical vapor deposition
摘要： We report enhanced gate stack stability in GaN metal insulator semiconductor high electron mobility transistors (MISHEMTs) by using a bilayer SiNx as the gate dielectric. To obtain the bilayer gate dielectric scheme, a thin Si-rich SiNx interlayer was deposited before a high-resistivity SiNx layer by low pressure chemical vapor deposition. The Si-rich SiNx can effectively suppress the trapping phenomenon at the interface of the dielectric/AlGaN barrier. The upper high-resistivity SiNx layer can greatly block the gate leakage current to enable a large gate swing. Compared with the MISHEMTs using a single Si-rich or high-resistivity SiNx layer, the MISHEMTs with a bilayer gate dielectric take the advantages of both, realizing a gate stack with a stable threshold voltage and low leakage current. These results thus present great potential for developing high-performance GaN MISHEMTs using the bilayer SiNx gate dielectric scheme for highly ef?cient power applications.
关键词： LPCVD,SiNx,bilayer,gate dielectric,MISHEMTs,GaN
更新于2025-09-04 15:30:14