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Barrier height modification in Au/Ti/n-GaAs devices with a $$\hbox {HfO}_{2}$$HfO2 interfacial layer formed by atomic layer deposition
摘要： X-ray photoelectron spectroscopy has been carried out to characterize the surface of the hafnia (HfO2) thin films grown on n-GaAs wafer by atomic layer deposition, and the surface morphology of the HfO2 layer on GaAs has been analysed using atomic force microscopy. The barrier height (BH) values of 1.03 and 0.93 eV (300 K) for the Au/Ti/HfO2/n-GaAs structures with 3- and 5-nm HfO2 interfacial layers, respectively, have been obtained from the I–V characteristics of the devices, which are higher than the value of 0.77 eV (300 K) for the Au/Ti/n-GaAs diode fabricated by us. Therefore, it can be said that the HfO2 thin layer at the metal/GaAs interface can also be used for BH modification as a gate insulator in GaAs metal-oxide semiconductor (MOS) capacitors and MOS field-effect transistors. The ideality factor values have been calculated as 1.028 and 2.72 eV at 400 and 60 K; and as 1.04 and 2.58 eV at 400 and 60 K for the metal–insulating layer–semiconductor (MIS) devices with 3- and 5-nm interfacial layers, respectively. The bias-dependent BH values have been calculated for the devices by both Norde’s method and Gaussian distribution (GD) of BHs at each sample temperature. At 320 K, the (cid:2)b(V ) value at 0.70 V for a 3-nm MIS diode is about 1.08 eV from the (cid:2)b(V ) vs. V curve determined by the GD, and about 0.99 eV at 0.58 V for a 5-nm MIS diode. It has been seen that these bias-dependent BH values are in close agreement with those obtained by Norde’s method for the same bias voltage values.
关键词： metal–insulating layer–semiconductor (MIS) device,Barrier height modification and inhomogeneous,bias-dependent barrier height,temperature-dependent MIS diode parameters,atomic layer deposition (ALD)
更新于2025-09-23 15:23:52
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Decoupling Effects of Surface Recombination and Barrier Height on p-Si(111) Photovoltage in Semiconductor|Liquid Junctions via Molecular Dipoles and Metal Oxides
摘要： This work provides insight into carrier dynamics in a model photoelectrochemical system comprised of a semiconductor, metal oxide, and metal. To isolate carrier dynamics from catalysis, a common catalytic metal (Pt) is used in concert with an outer-sphere redox couple. Silicon (111) substrates were surface-functionalized with electronegative aryl moieties (p-nitrophenyl and m-dinitrophenyl). A mixed monolayer using p-nitrophenyl/methyl exhibited high surface quality as determined by X-ray photoelectron spectroscopy (low surface SiOx content) and low surface recombination velocity. This substrate also exhibited the expected positive surface dipole, as evidenced by rectifying J?V behavior on p-type substrates, and by positive photovoltage measured by surface photovoltage spectroscopy. Its close molecular relative m-dinitrophenyl exhibited poor electronic surface quality as indicated by high SiOx coverage and high surface recombination velocities (S > 3000 cm s?1). Photoelectrochemical J?V measurements of p-type Si-functionalized surfaces in contact with a high concentration (50 mM) of methyl viologen (MV2+) in aqueous media revealed VOC values that are correlated with the measured barrier heights. In contrast, low-concentration (1.5 mM) MV2+ experiments revealed significant contributions from surface recombination. Next, the electronic and (photo)electrochemical properties were studied as a function of ALD metal oxide deposition (TiO2, Al2O3) and Pt deposition. For the m-dinitrophenyl substrate, ALD deposition of both TiO2 and Al2O3 (150 °C, amorphous) decreased the surface recombination velocity. Surprisingly, this TiO2 deposition resulted in negative shifts in VOC for all surfaces (possibly ALD-TiO2 defect band effects). However, Pt deposition recovered the efficiencies beyond those lost in TiO2 deposition, affording the most positive VOC values for each substrate. Overall, this work demonstrates that (1) when carrier collection is kinetically fast, p-Si(111)?R devices are limited by thermal emission of carriers over the barrier, rather than by surface recombination. And (2) although TiO2 |Pt improves the PEC performance of all substrates, the beneficial effects of the underlying (positive) surface dipole are still realized. Lastly (3) Pt deposition is demonstrated to provide beneficial charge separation effects beyond enhancing catalytic rates.
关键词： solar fuels,interfacial dipole,atomic layer deposition (ALD),surface functionalization,band-edge modulation,photoelectrochemistry
更新于2025-09-23 15:22:29
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A comparison of the morphological and electrical properties of sol-gel dip coating and atomic layer deposition of ZnO on 3D nanospring mats
摘要： We report on the morphological and electrical properties, with (light) and without (dark) UV illumination, of conformal coatings of ZnO on silica nanosprings deposited by sol-gel and atomic layer deposition (ALD) for the first time. Field Emission Scanning Electron Microscopy (FESEM) imaging showed that both methods produce conformal coatings of ZnO on the nanosprings. The surface of the sol-gel coatings exhibited cracks at higher numbers of dipping/sintering cycles, while the morphology of ALD ZnO films were always smooth and devoid of cracks. The effective photoconductivity of the sol-gel ZnO coated nanospring mats increased nonlinearly with increasing coating thickness. The corresponding dark effective conductivity of the sol-gel ZnO coated nanospring mats also increased within the same thickness range. Alternatively, the effective photoconductivity of the ALD ZnO coated nanospring mats increased linearly with increasing coating thickness. The corresponding dark effective conductivity also increased within the same thickness range. The superior effective conductivity and photoconductivity of the ALD ZnO coated nanospring mats is attributed to the uniformity of the coating and the absence of cracks, which are observed for the thicker sol-gel ZnO coatings.
关键词： atomic layer deposition (ALD),semiconductors,sol-gel,nanosprings,field emission scanning electron microscopy,conductivity,ZnO
更新于2025-09-23 15:22:29
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Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires
摘要： In this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7–14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study of photoluminescence (PL) spectra of SiNWs/ZnO samples showed the domination of defect emission bands, pointing to deviations of the stoichiometry of the prepared 3D ZnO nanostructures. Reduction of the PL intensity of the SiNWs/ZnO with the increase of SiNWs etching time was observed, depicting an advanced light scattering with the increase of the nanowire length. These results open up new prospects for the design of electronic and sensing devices.
关键词： nanosphere lithography (NSL),atomic layer deposition (ALD),Silicon nanowires (SiNWs),metal-assisted chemical etching (MACE),ZnO
更新于2025-09-23 15:21:21
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Investigation of the Physical Properties of Plasma Enhanced Atomic Layer Deposited Silicon Nitride as Etch Stopper
摘要： Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiNx) films remain largely unresearched. Achieving a low WER of a SiNx film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiNx using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiNx films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270 °C – 360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Varying hydrogen concentration and differences in the hydrogen bonding states resulted in different bulk film densities, and accordingly, a variation in WER. We observe a linear relationship between hydrogen bonding concentration and WER as well as a reciprocal relationship between bulk film density and WER. Analogous to the PECVD SiNx processes, a reduction in hydrogen bonding concentration arises from either (1) thermal activation or (2) plasma excited species. However, unlike the case with silane (SiH4)-based PECVD SiNx, PEALD SiNx WERs are affected by residual impurities of Si precursors (i.e., chlorine impurity). Thus, possible wet etching mechanisms in HF in which the WER is affected by hydrogen bonding states or residual impurities are proposed. The shifts of amine basicity in SiNx due to different hydrogen bonding states and the changes in Si electrophilicity due to Cl impurity content are suggested as the main mechanisms that influence WER in the PEALD processes.
关键词： plasma-enhanced ALD (PEALD),bulk film density,hexachlorodisilane (HCDS),wet etch rate (WER),silicon nitride,hydrogen/chlorine content,atomic layer deposition (ALD),hydrogen bonding state
更新于2025-09-23 15:21:01
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Local atomic structure of the GaN-side of the Al2O3/GaN interface revealed by X-ray absorption spectroscopy
摘要： The interface between a gate insulator (Al2O3) and a semiconductor (GaN) was investigated via surface-sensitive Ga K-edge extended X-ray absorption fine structure spectroscopy, achieved by detecting the Ga LMM Auger electrons originated from the Ga K-shell absorption. This GaN-side interface study was conducted on Al2O3 thin films formed via atomic layer deposition. The determined atomic structures revealed GaN crystalline changes and the formation of Ga–O bonds due to nitrogen annealing.
关键词： Aluminum oxide (Al2O3),Interface,Post-deposition annealing (PDA),Gallium nitride (GaN),Extended X-ray absorption fine structure (EXAFS),Atomic layer deposition (ALD)
更新于2025-09-19 17:13:59
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Processing of AC-coupled n-in-p pixel detectors on MCz silicon using atomic layer deposited aluminium oxide
摘要： We report on the fabrication of capacitively (AC) coupled n+-in-p pixel detectors on magnetic Czochralski silicon substrates. In our devices, we employ a layer of aluminium oxide (Al2O3) grown by atomic layer deposition (ALD) as dielectric and field insulator, instead of the commonly used silicon dioxide (SiO2). As shown in earlier research, Al2O3 thin films exhibit high negative oxide charge, and can thus serve as a substitute for p-stop/p-spray insulation implants between pixels. In addition, they provide far higher capacitance densities than SiO2 due to their high dielectric constant, permitting more efficient capacitive coupling of pixels. Furthermore, metallic titanium nitride (TiN) bias resistors are presented as an alternative to punch-through or poly-Si resistors. Devices obtained by the above mentioned process are characterized by capacitance–voltage and current–voltage measurements, and by 2 MeV proton microprobe. Results show the expected high negative charge of the Al2O3 dielectric, uniform charge collection efficiency over large areas of pixels, and acceptable leakage current densities.
关键词： Capacitive coupling,Al2O3,Atomic layer deposition (ALD),Pixel detector
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Pulsed Power & Plasma Science (PPPS) - Orlando, FL, USA (2019.6.23-2019.6.29)] 2019 IEEE Pulsed Power & Plasma Science (PPPS) - 2D Simulations of the NS-Laser Shock Peening
摘要： We report on the impact of H2 high-pressure annealing (HPA) onto In0.7Ga0.3As MOSCAPs and quantum-well (QW) MOSFETs with Al2O3/HfO2 gate-stack. After HPA with process condition of 300 °C, H2 ambient and pressure of 20 atm, we observed notable improvements of the capacitance–voltage (CV) characteristics in InGaAs MOSCAPs with Al2O3/HfO2 gate-stack, such as reduction of equivalent-oxide-thickness and less frequency dispersion in the accumulation region. There was 20% improvement of the interfacial trap density ( Dit). Then, we incorporated the HPA process into the fabrication of sub-100-nm In0.7Ga0.3As QW MOSFETs, to investigate the impact of HPA process. After HPA process, the device with L g = 50 nm exhibits improved subthreshold-swing (SS) = 105 mV/decade, in comparison with SS = 130 mV/decade for the reference device without HPA process. Finally, we carried out reliability assessment under a constant-voltage-stress (CVS), and it turns out that the HPA process was effective in mitigating a shift of threshold voltage ((cid:2)VT ) during the CVS. These are attributed to the effective passivation of oxide traps in the high-k dielectric layer and interfacial traps, after HPA process in the H2 ambient.
关键词： interfacial trap density (Dit),subthreshold-swing (SS),high-pressure annealing,atomic layer deposition (ALD),InGaAs MOSFET
更新于2025-09-19 17:13:59
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P‐9.1: QD based color converter with DBR Structure and its application on Micro‐LED
摘要： An enhancement of light extraction efficiency of quantum dots (QD) (LEDs) with Bi-functional TiO2/Al2O3 distributed Bragg reflector (DBR) nanolaminate structure grown by atomic layer deposition (ALD) has been demonstrated. The DBRs were simulated and optimized with TFCalc, and they exhibited excellent and tunable optical properties, as well as reliable moisture barrier performance. These DBRs were integrated in the QD-LED, enabling an obvious increase in red emission and a strong decrease in blue light transmittance, which can achieve color conversion greatly. Furthermore, these DBRs can prolong the lifetime of QDs evidently by isolating the QDs from the moisture vapor. These results highlight the potential application of DBRs in the QLEDs and QD-LEDs.
关键词： atomic layer deposition (ALD),simulation,distributed Bragg reflector (DBR),water vapor transmission rates (WVTR),light extraction efficiency
更新于2025-09-19 17:13:59
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Plasma enhanced atomic layer deposition of plasmonic TiN ultrathin films using TDMATi and NH3
摘要： Transition metal nitrides, like titanium nitride (TiN), are promising alternative plasmonic materials. Here we demonstrate a low temperature plasma‐enhanced atomic layer deposition (PE‐ALD) of non‐stoichiometric TiN0.71 on lattice‐matched and ‐mismatched substrates. The TiN was found to be optically metallic for both thick (42 nm) and thin (11 nm) films on MgO and Si <100> substrates, with visible light plasmon resonances in the range of 550–650 nm. We also demonstrate that a hydrogen plasma post‐deposition treatment improves the metallic quality of the ultrathin films on both substrates, increasing the ε1 slope by 1.3 times on MgO and by 2 times on Si (100), to be similar to that of thicker, more metallic films. In addition, this post‐deposition was found to tune the plasmonic properties of the films, resulting in a blue‐shift in the plasmon resonance of 44 nm on a silicon substrate and 59 nm on MgO.
关键词： optical properties,plasmonics,atomic layer deposition (ALD),thin film,titanium nitride
更新于2025-09-16 10:30:52