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We demonstrate a novel method using electric field cycling to induce a phase transition in HfxZr1−xO2 to reach the morphotropic phase boundary of tetragonal and orthorhombic phase. Conventional methods used to induce the phase transition, such as high temperature annealing, cannot be used with the DRAM cell capacitor fabrication process because it associates with grain enlargement, increased leakage current, and a narrow process margin due to the metastability of the morphotropic phase boundary. To achieve an morphotropic phase boundary in HfxZr1−xO2 without high temperature annealing and without increasing leakage current, we propose a two-step process, using low temperature annealing to form the tetragonal phase and electric field cycling to achieve the morphotropic phase boundary of tetragonal and orthorhombic phase in HfxZr1−xO2 film. This approach enabled us to achieve both low voltage with high dielectric k value, and low leakage current, meeting the requirements for the next-generation DRAM cell capacitor dielectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Surface incorporation at the interface between atomic-layer-deposited Al2O3 thin film and AlGaN/GaN heterostructure was studied based on the understanding of charge configuration and electronic band structure through fabrication and numerical simulation. The annealing in H2S ambient at various temperatures prior to deposition of Al2O3 gate insulator incorporated the sulfur. The Al2O3 was formed on the sulfur treated GaN cap/AlGaN barrier/GaN by trimethylaluminum and water-based atomic layer deposition. Thereafter, TiN electrode was sputtered on the Al2O3, which was followed by forming gas annealing. The time-of-flight secondary ion mass spectroscopy disclosed that the sulfur located at the interface of Al2O3/GaN cap, of which concentration increased with annealing temperature. Positive charges at the interface of Al2O3/GaN cap induced by sulfur increased the two-dimensional electron gas density and shifted the pinch-off voltage in the negative direction. The diffusion of sulfur in the GaN cap and AlGaN barrier can hamper the electron accumulation under positive gate voltage and shifts the accumulation voltage of the spillover region in the positive direction. Furthermore, the incorporated sulfur suppressed the gate leakage current.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The effects of sulfur passivation of the Ge substrate were studied through (NH4)2S solution treatment and the rapid thermal annealing under an H2S atmosphere prior to atomic-layer-deposition (ALD) of HfO2. While a chemically unstable and uneven sulfur layer was formed by (NH4)2S solution treatment, a stable, highly uniform and dense sulfur layer with a thickness of ∼2 nm was formed by H2S annealing on Ge substrates. The sulfur concentration at the interface increased with H2S annealing temperature. Sulfur passivation suppressed the diffusion of Ge into the HfO2 film and any interfacial layer growth during ALD, which resulted in a decreased equivalent oxide thickness of gate insulator. The interface properties, such as interface defect state density and hysteresis in capacitance–voltage behavior, were also improved by sulfur passivation through H2S annealing. H2S annealing is much more compatible with a mass-production process compared to the conventional (NH4)2S solution treatment process. [ABSTRACT FROM AUTHOR]

Sulfur was embedded in atomic-layer-deposited (ALD) HfO2 films grown on Ge substrate by annealing under H2S gas before and after HfO2 ALD. The chemical states of sulfur in the film were examined by S K-edge X-ray absorption spectroscopy. It was revealed that the valences of S-ions were mostly -2 at Ge/HfO2 interface (GeS x or HfO2- yS y to passivate the interface), while they were mostly +6 in HfO2 layers (sulfates; HfO2- z(SO4) z). The leakage current density in post-deposi-tion-treated film was lower than that in pre-deposition-treated one. This suggests that the passivation of defects in oxide layer by sulfate ions is more effective to lower the leakage current rather than the interface defect passivation by S2- ions. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The influence of two oxygen source types, H2O and O3, on residual C‐related impurities in atomic‐layer‐deposited (ALD) Al2O3 film is systematically examined. ALD Al2O3 film grown using H2O contains negligible C‐related impurities irrespective of growth temperature. However, the C‐related impurity in film grown using O3 exhibits strong dependence on growth temperature; only Al carbonate (Al‐CO3) is present in film grown at 300 °C, but C‐related impurities with lower oxidation states, such as Al‐COOH and Al‐CHO, appear as the temperature decreases to 150 °C. This suggests that the reactivity of O3 and H2O in the ALD process has a different temperature dependence; from a residual impurity perspective, compared to O3, H2O is a beneficial oxygen source for low temperature processes. Electrical properties, such as charge trapping and gate leakage current, are also examined. For a growth temperature of 300 °C, the film grown using O3 is slightly superior to the film grown using H2O due to its high film density. However, the film grown using H2O demonstrates better electrical characteristics at low growth temperature, 150 °C. Atomic layer deposited Al2O3 film grown using H2O contains negligible C impurities irrespective of growth temperature. However, the C impurity in film grown using O3 increased with decreasing growth temperature. The reactivity of O3 and H2O in the atomic layer deposition (ALD) process has a different temperature dependence. From a residual impurity perspective, H2O is a beneficial oxygen source for low temperature ALD compared to O3. [ABSTRACT FROM AUTHOR]

We demonstrated how the photoelectrochemical (PEC) performance was enhanced by conformal deposition of an amorphous molybdenum sulfide (a-MoS x ) thin film on a nanostructured surface of black Si using atomic layer deposition (ALD). The a-MoS x is found to predominantly consist of an octahedral structure (S-deficient metallic phase) that exhibits high electrocatalytic activity for the hydrogen evolution reaction with a Tafel slope of 41 mV/dec in an acid electrolyte. The a-MoS x has a smaller work function (4.0 eV) than that of crystalline 2H-MoS 2 (4.5 eV), which induces larger energy band bending at the p-Si surface, thereby facilitating interface charge transfer. These features enabled us to achieve an outstanding kinetic overpotential of ∼0.2 V at 10 mA/cm 2 and an onset potential of 0.27 V at 1 mA/cm 2 . Furthermore, the a-MoS x layer provides superior protection against corrosion of the Si surface, enabling long-term PEC operation of more than 50 h while maintaining 87% or more performance. This work highlights the remarkable advantages of the ALD a-MoS x layer and leads to a breakthrough in the architectural design of PEC cells to ensure both high performance and stability.

We demonstrated surface passivation of a black Si-based solar cell using an (NH 4 ) 2 S solution to mitigate surface recombination velocity. Incorporated S at the interface between atomic-layer-deposited Al 2 O 3 and black Si by (NH 4 ) 2 S solution treatment boosted the density of negative fixed charges, S-enhanced field-effect passivation. Furthermore, NH 4 OH generated during (NH 4 ) 2 S solution treatment removed the defective Si phase at the black Si surface, the surface cleaning effect. The optimized (NH 4 ) 2 S solution treatment significantly enhanced the internal quantum efficiency up to ∼17.2% in the short wavelength region, suggesting suppressed surface recombination. As a result, photoconversion efficiency of the cell increased from 11.6 to 13.5%, by 16% compared to the control cells without (NH 4 ) 2 S solution treatment.