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Trisilylamine (TSA), an exemplary chlorine and carbon-free commercial silylamine precursor, is well-known to induce improvements in the process and properties of silicon nitride (SiNx) thin films grown using atomic layer deposition (ALD). Herein, we report a TSA homolog, tris(disilanyl)amine (TDSA), as a novel chlorine and carbon-free precursor for the deposition of highly etch resistant SiNx thin films having a high growth rate at a low temperature (

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 (270–360 °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. Va...

In this letter, we report gallium nitride-based metal-insulator-semiconductor high-electron-mobility transistors (GaN MIS-HEMTs) with a 16-nm-thick silicon nitride (SiN x ) gate insulator and surface passivation layer grown using low-temperature (300 °C) hollow cathode plasma-enhanced atomic layer deposition. Tris(dimethylamino) silane and a remote N2 plasma were used as the silicon precursor and the nitrogen co-reactant, respectively. Though the growth temperature was as low as 300 °C, we obtained excellent film properties such as a high refractive index (2.00), a high film density (2.9 g/cm3), and a low wet etch rate (0.8 nm/min) in 100:1 hydrofluoric acid. High-resolution transmission electron microscopy images of the gate stacks showed ~1.5 nm $\beta $ -phase Si3N4 crystalline interfacial layer on the GaN surface. The devices showed a negligible hysteresis of ~50 mV, a steep subthreshold slope of 76 mV/dec, and a high ON/OFF drain current ratio of ~109. In addition, the devices showed a small positive/negative bias temperature threshold voltage ( ${V}_{\text {th}}$ ) instability ( $\Delta {V}_{\text {th}}\le 0.2$ V at 25 °C and 150 °C) as well as a mitigated current collapse under an off-state quiescent ${V}_{\text {DS}}$ of 20 V.

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSi2Cl5), was investigated for the growth of silicon nitride (SiNx) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270–360 °C. At identical process conditions, PCDS not only demonstrated approximately >20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (Si2Cl6), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiNx films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (

The effects of post-metallization annealing (PMA) have been investigated for thermally-grown SiO2 on 4H-SiC metal-oxide-semiconductor (MOS) with a molybdenum (Mo) gate electrode. Mo is a great metal gate material for Silicon carbide (SiC) due to its high thermal budget and low thermal expansion coefficient, which allows high-temperature processing after the gate electrode formation. In this study, PMA process was carried out after Mo gate formation on thermally-grown SiO2/4H-SiC in the temperature range from 600 to 1000 °C in N2 or a forming gas ambient. The fabricated Mo/SiO2/4H-SiC MOS device annealed at 800 °C exhibited excellent interface characteristics with negligible hysteresis in comparison with as-grown or post-oxidation annealed samples.

We have developed a nitrogen-incorporated silicon oxide (SiOxNy) deposition process using plasma enhanced atomic layer deposition (PEALD) for the gate insulator of recessed-gate Al-GaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. The SiOxNy film deposited on a recessed GaN surface exhibited a breakdown field of 13.2 MV/cm and a conduction band offset of 3.37 eV, which are the highest values reported for GaN MIS structures to the best of our knowledge. The fabricated normally-off transistor exhibited very promising characteristics such as a threshold voltage of 2.2 V, a maximum drain current density of 428 mA/mm, and a breakdown voltage of 928 V.

Nanodiamonds hosting colour centres are a promising material platform for various quantum technologies. The fabrication of non-aggregated and uniformly-sized nanodiamonds with systematic integration of single quantum emitters has so far been lacking. Here, we present a top-down fabrication method to produce 30.0$\pm$5.4 nm uniformly-sized single-crystal nanodiamonds by block copolymer self-assembled nanomask patterning together with directional and isotropic reactive ion etching. We show detected emission from bright single nitrogen vacancy centres hosted in the fabricated nanodiamonds. The lithographically precise patterning of large areas of diamond by self-assembled masks and their release into uniformly sized nanodiamonds open up new possibilities for quantum information processing and sensing., Comment: 15 pages, 2 figures

Here, we theoretically and experimentally investigate the impact of a high- $\kappa $ layer inserted between graphene and p-Si in a graphene/Si junction. We have achieved 86-fold and 222-fold reductions in a specific contact resistivity ( $\rho _{c}$ ) by inserting 1-nm-thick Al2O3 and 2-nm-thick TiO2 in the graphene–semiconductor junction, respectively, corresponding to lowering the effective barrier height by 0.24 and 0.12 eV. Furthermore, we propose a graphene-induced gap state model that simultaneously considers the graphene’s modulation by a gate bias and the effect of the high- $\kappa $ insertion.

The effects of ALD ZnO passivation of ammonium hydroxide cleaned p-In0.53Ga0.47As is studied in detail with in-situ x-ray photoelectron spectroscopy (XPS), and metal-oxide-semiconductor capacitors (MOSCAPs) are fabricated in order to judge the effectiveness of ZnO as a passivation layer. Diethylzinc (DEZ) and water are used as precursors. Multiple DEZ pulses are used in the first ALD cycle in order to determine the oxide cleanup ability of DEZ. XPS results indicate that DEZ can chemically reduce Ga3+ and As5+ to Ga1+ and As3+ respectively, with the majority of change occurring before the first water pulse. DEZ is found to have minimal oxide cleanup ability, with the overall the amount of As oxide reduced by approximately 15% and Ga oxide remaining unchanged. ZnO passivated MOSCAPs with HfO2 dielectric show significant improvement over MOSCAPs without ZnO passivation. Accumulation frequency dispersion, hysteresis and D it are all reduced dramatically.

High-voltage AlGaN/GaN Schottky barrier diodes (SBDs) were fabricated using on a silicon (1 1 1) substrate, and a post-process O2 treatment was carried out to reduce the leakage current and increase the breakdown voltage. Time-of-flight secondary ion mass spectroscopy revealed that, following the post-process O2 treatment, oxygen diffused into an AlGaN barrier and AlO was generated. A significant suppression of the leakage current (of approximately 6 orders of magnitude) occurred in the buffer isolation structures following the O2 treatment. Our method also resulted in suppression of the surface leakage current through the mesa-etched surface. A virgin GaN SBD exhibited a leakage current of 1.76 × 10−2 A/cm2, whereas the equivalent O2-treated device had a leakage current of 1.75 × 10−4 A/cm2 (the anode–cathode distance was LAC = 10 μm, and the applied bias was −100 V). This reduction in the leakage current was caused by surface passivation at the anode and cathode. The post-process O2 treatment also increased the breakdown voltage from Vb = 808 V to Vb = 1590 V for a device with LAC = 10 μm. GaN SBDs with and without the post-process O2 treatment exhibited low specific on-resistance of Ron,sp = 2.51 mΩ cm2 and Ron,sp = 2.48 mΩ cm2, respectively, with LAC = 10 μm. Devices with the post-process O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 1006 MW/cm2, whereas devices without the O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 263 MW/cm2. These high-voltage GaN SBDs employing the post-process O2 treatment are suitable for applications including DC–DC converters, inverters, and power factor correction circuits, where high voltage operation is required with low leakage currents.

Atomic-layer-deposited La

We studied the impact of H2 pressure during post-metallization annealing on the chemical composition of a HfO2/Al2O3 gate stack on a HCl wet-cleaned In0.53Ga0.47As substrate by comparing the forming gas annealing (at atmospheric pressure with a H2 partial pressure of 0.04 bar) and H2 high-pressure annealing (H2-HPA at 30 bar) methods. In addition, the effectiveness of H2-HPA on the passivation of the interface states was compared for both p- and n-type In0.53Ga0.47As substrates. The decomposition of the interface oxide and the subsequent out-diffusion of In and Ga atoms toward the high-k film became more significant with increasing H2 pressure. Moreover, the increase in the H2 pressure significantly improved the capacitance‒voltage characteristics, and its effect was more pronounced on the p-type In0.53Ga0.47As substrate. However, the H2-HPA induced an increase in the leakage current, probably because of the out-diffusion and incorporation of In/Ga atoms within the high-k stack.

We investigated ZnO surface passivation of a GaAs (100) substrate using an atomic layer deposition (ALD) process to prepare an ultrathin ZnO layer prior to ALD-HfO2 gate dielectric deposition. Significant suppression of both Ga-O bond formation near the interface and As segregation at the interface was achieved. In addition, this method effectively suppressed the trapping of carriers in oxide defects with energies near the valence band edge of GaAs. According to electrical analyses of the interface state response on p- and n-type GaAs substrates, the interface states in the bottom half of the GaAs band gap were largely removed. However, the interface trap response in the top half of the band gap increased somewhat for the ZnO-passivated surface.

This paper presents the experimental torque disturbance analysis of a missile hatch system by spline backlash. The missile hatch system uses a spline and gear train for vertical elevation of the heavy hatch. The spline used for the rotation shaft of the hatch is generally used for automotive driving parts that transmit high amounts of power. It has an angular backlash, which results in jerks. Backlash of the hatch spline influences hatch swinging. The spline backlash and hatch swing are experimentally analyzed by measuring the hatch's rotation angle and acceleration. Hatch swing is visually observable for a short period, and it is measured by measuring the rotation angle variation and hatch acceleration. The shape of fluctuation and duration time of hatch angle variation are similar to those of torque. This shows that the hatch swing due to spline backlash generates torque disturbances. Corresponding Author, eskang@cnu.ac.kr 2014 The Korean Society of Mechanical Engineers C

With the continued miniaturization of devices in the semiconductor industry, atomic layer deposition (ALD) of silicon nitride thin films (SiNx) has attracted great interest due to the inherent benefits of this process compared to other silicon nitride thin film deposition techniques. These benefits include not only high conformality and atomic-scale thickness control, but also low deposition temperatures. Over the past 20 years, recognition of the remarkable features of SiNx ALD, reinforced by experimental and theoretical investigations of the underlying surface reaction mechanism, has contributed to the development and widespread use of ALD SiNx thin films in both laboratory studies and industrial applications. Such recognition has spurred ever-increasing opportunities for the applications of the SiNx ALD technique in various arenas. Nevertheless, this technique still faces a number of challenges, which should be addressed through a collaborative effort between academia and industry. It is expected that the SiNx ALD will be further perceived as an indispensable technique for scaling next-generation ultra-large-scale integration (ULSI) technology. In this review, the authors examine the current research progress, challenges and future prospects of the SiNx ALD technique.

In this paper, the disturbance applied to launcher hatch by ship motions is introduced to identify the vertical ship motion disturbance. Basically, ship motions are comprised of 6 degrees of freedom: roll, pitch, yaw, heave, surge and sway. In the case of the shipboard launcher hatch the coupled pitch, heave and roll are significant motions to be transformed to a vertical direction motion. The maximum acceleration values are obtained from the vertical motion model and the ship motion data in accordance with ship type and hatch location on the ship. We verify that the maximum pitch motion mainly influences the launcher hatch and also present the quantity of the maximum load disturbance by the ship’s motion acceleration. Keywords: ship motion, 6-DOF, vertical motion model, load disturbance, launcher hatch I. 서론 함정에 탑재되는 일반적인 전기기계 구동장치 및 제어기로 구성되는 함정 시스템은 함정운용 특성에 따른 다양한 외란(disturbance)을 받게 되며 함운용 외란을 제거하기 위한 제어기 설계가 요구된다. 함정 시스템 설계에 필요한 함운용 외란을 실제적으로 측정하여 제어기에 전달하는 경우 시스템 설계가 복잡해지고 고가의 비용이 든다. 따라서 함운용 외란을 잘 분석하여 함정 시스템 설계에 적용한다면 시스템 설계 및 성능 평가에도 유리하고, 설계 및 제작 비용도 절감할 수 있다. 함정에 탑재되는 제어시스템에 작용하는 외란 요소들은 함정종류(ship type) 및 해면상태(sea state)에 의해 결정되는 함정운동(ship motion), 함정의 운항속도(ship speed), 해상에서 부는 바람속도(wind velocity), 적설부하/결빙(icing) 및 함정의 엔진으로부터 전달되는 함진동(ship vibration) 등으로 다양한 형태를 갖는다. 이와 같은 외란 요소들은 함정에 설치되는 안정화 장치(stabilizer) 설계, 유도탄 발사 시의 유도탄 초기 안정성 해석 및 함정 발사대 해치시스템 설계 등에 고려되어야 하는 중요한 설계 요소이다. 특히 함운용시 필수적으로 함정 시스템에 직접 영향을 주는 외란은 함정운동으로 회전운동인 롤(roll), 피치(pitch), 요(yaw) 운동과 병진운동인 히브(heave), 서지(surge), 스웨이(sway) 운동으로 6자유도 운동으로 구성된다. 함정 시스템 설계를 위하여 이러한 함정운동 외란에 대한 식별(identification), 해석(analysis), 추정(estimation) 및 예측(prediction)에 관한 연구가 많이 수행되고 있다. 함정운동과 관련한 주요 연구들로 함정 형상 설계, 함정 운항제어, 함정운동에 대한 보상 및 제어응용을 위한 수학적 모델링 및 시뮬레이션 기법 등이 많이 연구되어 왔다[1,2,10, 11]. 함정운동은 실제 측정한 데이터를 분석하여 예측이 가능하지만 여러 운동이 중첩되어 있어 신경망(neural) 네트워크를 사용하여 조합(couple)된 함정운동에 관한 연구도 수행되었다[3]. 또한 함정에서 유도탄을 발사하기 위해서는 함정운동 외란을 고려한 유도탄 발사 초기 거동에 대한 안정성 해석이 중요하므로 함정운동 외란을 확률변수로 적용하여 유도탄 발사 안정성에 관한 연구도 수행되었다[4]. 함정 갑판에 항공기 착륙을 위하여 칼만 필터를 사용하여 실시간 함정운동을 추정하였으며[5], 또한 ISAR (Inverse Synthetic Aperture Radar) 데이터를 측정하여 함정운동을 추정하는 기법을 제시하였다[6]. 본 논문에서는 함정의 COG (Center of Gravity) 또는 COF (Center of Floating)에 작용하는 함정운동 데이터를 사용하여 함정에 탑재되는 발사대 해치에 작용하는 함정운동 외란에 대해서 분석하고, 함정운동 가속도에 의해 발생되는 부하 외란의 크기를 제시하여 해치시스템 설계 및 제어기 설계에 활용할 수 있도록 한다. II. 함정운동 분석 1. 좌표시스템 및 기본개념 그림 1은 함정운동을 나타내기 위한 좌표시스템으로 함정 운동의 중심점인 COG 또는 COF 기준의 X, Y, Z 좌표와 함정에 탑재되는 발사대 해치 COG기준의 x, y, z 좌표로 나타내었다. 그림 2는 함정의 COF 기준축을 중심으로 발생되는 함정의 6자유도 운동 방향을 나타낸다. 6자유도 함정운동은 히브, 서지, 스웨이 병진운동과 롤, 피치, 요 회전운동으로 구성된다. 발사대 해치에 전달되는 함정운동은 함정 중심점에서의 함정운동 모델과 함정 중심점에서의 발사대 탑재 위치를 사용하여 계산할 수 있다. 함정운동 모델은 일반적으로 정현모델(sinusoidal model)과 과도모델(transient model)을 사용한다. 정현모델은 함정의 종

The physical and electrical effects caused by interfacial reactions of HfO2 on Si-passivated GaAs were investigated by various methods. The results showed that the Si layer decreases the diffusion and formation of Ga O. Moreover, post-nitridation in HfO2/Si/GaAs significantly reduced the formation of As O and Ga O. The depth profiling data showed that two separated layered structures were formed with HfO2 and a mixture of HfO2 and SiO2 after the annealing process. The crystalline structure and formation of Ga O in the film affect the band offsets between GaAs and the high-k HfO2 dielectric. Moreover, the Si passivation effectively suppressed the interfacial defects caused by Ga O diffusion during the annealing treatment. The nitridation cause As diffusion to oxygen vacancy of HfO2 result in the increase of the interfacial defect.

The high-k gate dielectric structures in stacked (HfO2/Al2O3) and nanolaminated (HfAlOx) forms with a similar apparent accumulation capacitance were atomic-layer-deposited on n-type In0.53Ga0.47As substrates, and their electrical properties were investigated in comparison with a single-layered HfO2 film. Al-oxide interface passivation in both forms proved to be effective in preventing a significant In incorporation in the high-k film and reducing the interface state density. The measured valence band spectra in combination with the reflection electron energy loss spectra were used to extract the energy band parameters of various dielectric structures on In0.53Ga0.47As. A further decrease in the interface state density was achieved in the stacked structure than in the nanolaminated structure. However, in terms of the other electrical properties, the nanolaminated sample exhibited better characteristics than the stacked sample, with a smaller border trap density and lower leakage current under substrate injection conditions with and without voltage stressing.

The effect of the deposition temperature (200, 250, and 300 °C) on the electrical properties of the atomic-layer-deposited [atomic layer deposition (ALD)] HfO2 films on InP was studied. A significant grain growth as well as an increase in the accumulation capacitance occurred by increasing the ALD temperature from 200 to 250 °C. However, a further increase to 300 °C degraded the electrical properties as verified by various electrical characterizations, including an accumulation capacitance lowering, a near-interface defect (trap) formation, and an increase in the electrical stress-induced new trap generation, due to a significant In out-diffusion to the HfO2 film side.

We report on atomic layer deposited Hf0.5Zr0.5O2 (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm2) and a low FE saturation voltage (∼1.5 V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90 nm. The TiN films are deposited at room temperature and annealed at 400 °C in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures.

In order to achieve both interfacial oxide reduction and exible work function control by using a single gate electrode structure, we deposited Ni/Ti bi-layered metal electrodes with di erent Ti thicknesses on Hf-silicate lms and investigated their electrical properties. A relatively small reduction of the interfacial oxide thickness (by 0.5 nm) when using the reactive Ti electrode was observed, possibly due to the lower oxygen di usivity in the Hf-silicate lm than in HfO2. No interfacial reaction between Ni and Ti was observed after post-metallization heat treatments at temperatures up to 400 C. The atband voltage shift from a pure Ni to a pure Ti electrode happened below a thickness of 6 nm for Ti and a gradual change of the e ective work function by 0.6 eV was obtained by further decreasing the underlying Ti thickness.

We studied the thermal stability of HfO2 on an InP structure when an Al2O3 interface passivation layer (PL) was introduced. In contrast to the thick (∼4 nm) Al2O3-PL, an almost complete disappearance of the thin (∼1 nm) Al2O3-PL was observed after a post-deposition anneal at 600 °C. Based on various chemical and electrical analyses, this was attributed to the intermixing of the thin Al2O3-PL with HfO2, which might have been accompanied by the out-diffusion of a substantial amount of substrate elements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The effects of both the deposition temperature and the HfO2 film thickness on the interfacial layer (IL) evolution were studied when tetrakis(ethylmethylamino)hafnium and H2O based atomic layer deposition (ALD) was performed on InP substrates. While the self-cleaning effect resulted in an IL-free structure after formation of ∼2 nm thick HfO2 at 200 °C and 250 °C, substantial IL growth occurred at 300 °C, probably due to simultaneous InP oxidation. Following further growth to ∼8 nm at 300 °C, the IL was almost removed and, in particular, a significant In incorporation into the HfO2 film was observed, which was attributed to IL decomposition and subsequent out-diffusion of the constituent elements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The effectiveness of trimethylaluminum (TMA) and tetrakis(dimethylamido)titanium (TDMAT) pretreatments on GaSb substrates were compared by examining the interfacial and capacitance–voltage (C–V) characteristics of Al2O3/p-type GaSb capacitors. In addition, for sample preparation, the temperature-dependent surface reactivity of GaSb was confirmed by examining the impact of the atomic layer deposition (ALD) loading temperature (stand-by temperature in air). An increase in the loading temperature from 65 to 150 °C in air ambient degraded the interfacial and C–V properties, which confirms the importance of the processing temperature for GaSb-based devices. Both in situ TMA and TDMAT pretreatments at 65 °C prior to the ALD of Al2O3 (150 °C) were effective in decreasing the amount of the interface oxide and the interface state density. While a similar degree of frequency dispersion in the C–V accumulation region was observed in the ALD-Al2O3/GaSb capacitor samples with and without TMA pretreatment, it largely increased for the TDMAT-pretreated sample, probably due to the formation of a Ti-oxide interlayer.

In this paper, the effect of atomic layer deposited ZrO2 gate dielectrics, deposited at low temperature (100 °C), on the characteristics of recessed-gate High Electron Mobility Transistors (HEMTs) on Al0.25Ga0.75N/GaN/Si is investigated and compared with the characteristics of those with ZrO2 films deposited at typical atomic layer deposited (ALD) process temperatures (250 °C). Negligible hysteresis (ΔVth 4 V), and low interfacial state density (Dit = 3.69 × 1011 eV−1 cm−2) were observed on recessed gate HEMTs with ∼5 nm ALD-ZrO2 films grown at 100 °C. The excellent properties of recessed gate HEMTs are due to the absence of an interfacial layer and an amorphous phase of the film. An interfacial layer between 250 °C-ZrO2 and GaN is observed via high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. However, 100 °C-ZrO2 and GaN shows no significant interfacial layer formation. Moreover, while 100 °C-ZrO2 films maintain an amorphous phase on either substrate (GaN and Si), 250 °C-ZrO2 films exhibit a polycrystalline-phase when deposited on GaN and an amorphous phase when deposited on Si. Contrary to popular belief, the low-temperature ALD process for ZrO2 results in excellent HEMT performance.

Atomic-layer-deposited La2O3 films were grown on Si with different O3 pulse times and growth temperatures. The interfacial reactions and impurity behaviors were observed using in situ X-ray photoelectron spectroscopy. Longer pulse time of O3 formed the solid SiO2 interfacial barrier layer, which suppressed La-silicate formation. Meanwhile, the carboxyl compound acting as an impurity phase was replaced with LaCO3 on increasing the O3 pulse time due to further oxidation and reaction of La. Higher growth temperatures enhanced La-silicate formation by mixed diffusion of Si and La2O3, during which most of the La2O3 phase was consumed at 400 °C. C and N impurities decreased with increasing growth temperature and completely disappear at 400 °C.

Atomic layer deposition is used to convert an (NH4)2S cleaned p-In0.53Ga0.47As with diethylzinc (DEZ) and water, resulting in the formation of a ZnO/ZnS interfacial passivation layer (IPL). The process is studied using in-situ X-ray photoelectron spectroscopy. DEZ reacts with sulfur and oxygen present on the surface, chemically reducing arsenic 3+ and gallium 3+ to lower oxidation states. The sulfur concentration remains constant during the deposition process while the oxygen concentration on the surface remains small, confirming that the IPL is composed of both ZnO and ZnS. Measurements of metal–oxide–semiconductor capacitors with HfO2 for the dielectric show that the ZnO/ZnS IPL can nearly eliminate frequency dispersion (D it in the 1011 eV−1 cm−2 range in the midgap. Frequency dispersion is observed in the depletion region and is attributed to minority carrier generation from the ZnO present in the IPL.

Amorphous Ti1−x Al x O y films in the Ti-oxide-rich regime (x < 0.5) were deposited on p-type GaAs via atomic layer deposition with titanium isopropoxide, trimethylaluminum, and H2O precursor chemistry. The electrical properties and energy band alignments were examined for the resulting materials with their underlying substrates, and significant frequency dispersion was observed in the accumulation region of the Ti-oxide-rich Ti1−x Al x O y films. Although a further reduction in the frequency dispersion and leakage current (under gate electron injection) could be somewhat achieved through a greater addition of Al-oxide in the Ti1−x Al x O y film, the simultaneous decrease in the dielectric constant proved problematic in finding an optimal composition for application as a gate dielectric on GaAs. The spectroscopic band alignment measurements of the Ti-oxide-rich Ti1−x Al x O y films indicated that the band gaps had a rather slow increase with the addition of Al-oxide, which was primarily compensated for by an increase in the valance band offset, while a nearly-constant conduction band offset with a negative electron barrier height was maintained.

The effect of Al2O3 mixing in HfO2 on the electrical properties was studied on InP substrates using nanolaminate films grown by atomic layer deposition. The In out-diffusion and the subsequent In-related oxide phase generation were effectively suppressed by introducing more Al2O3 to the HfO2 film. Although the decrease in the maximum capacitance was taken into consideration, more Al2O3 introduction significantly improved the dielectric properties. The magnitude of the capacitance–voltage frequency dispersion was decreased with the reduced border trap and interface state densities. Additionally, the leakage current characteristics were improved, including the voltage-stress-dependent reliability.

In this paper, we examined the effects of two different oxidants (H2O and O3) used during the atomic layer deposition (ALD) of HfO2 films on GaAs, particularly focusing on its interfacial and electrical properties. In comparison with the H2O-based ALD process, the O3-based process produced a large amount of elemental As and Ga–O related bonds near the HfO2/GaAs interface due to its stronger oxidizing power. High interface state and border trap densities of the O3-based sample degraded the low-field electrical stability, which was confirmed by the capacitance and leakage current measurements under various voltage-stressing conditions. However, in terms of high-field stability, the O3-based sample showed a much stronger resistance to stress-induced trap generation than the H2O-based sample.

This study reports the effects of the starting layer on the interface and electrical properties of HfAlOx films on GaAs, when the atomic layer deposition (ALD) was performed with tetrakis(ethylmethylamino)hafnium and trimethylaluminum precursors as well as an H2O oxidant. By using the Al2O3-first process, more decrease in the number of Ga–O bonds near the interface region was achieved than by using the HfO2-first process, which resulted in a reduction of the interface state density and the frequency dispersion. Furthermore, the Al2O3-first process decreased the border trap density, as well as the voltage stress-induced electron trapping, as estimated from the hysteresis characteristics of the capacitance–voltage and the leakage current measurement under a ramped-voltage stress condition. Based on these results, we experimentally demonstrate the importance of the cycling sequence during the ALD-HfAlOx process on GaAs.

This study presents an examination of the interfacial and electrical properties of HfO 2 films grown by plasma-enhanced atomic layer deposition with tetrakis(diethylmethylamino) hafnium and O 2 precursors on GaAs substrates cleaned with HF and then (NH 4 ) 2 S cleaning for three different dipping times. Systematic X-ray photoelectron spectroscopy analyses both before and after the HfO 2 deposition revealed that the optimal cleaning time in terms of the removal of the As- and Ga-oxides was significantly reduced by the partial "self-cleaning" process that occurred at a substantially lower deposition temperature of only 200°C, possibly due to the plasma effect. The frequency dispersion characteristics were strongly dependent on the cleaning method, however, the hysteresis characteristics were not.

Design, fabrication, and testing results of a hydrogen gas sensor based on a surface modified high density and high aspect ratio 3-D carbon post microarray are described in this paper. After the conversion of photoresist patterns into carbon electrodes, the increased surface was conformally coated with a metal oxide semiconductor film by atomic layer deposition (ALD). A maximum sensitivity as high as 100 (Rair/ Rhydrogen) has been observed in the fabricated sensor even in the presence of moisture at low temperature. A fast initial response (90% resistance drop in 30sec at 3000ppm hydrogen) of the sensor could be utilized for early leak detection. The methodology of surface modification as well as the test result shows good promise for various chemical sensing devices based on the proposed strategy.