The continuous improvement in the semiconductor industry has been successfully achieved by the reducing dimensions of CMOS (complementary metal oxide semiconductor) technology. For the last four decades, the scaling down of physical thickness of SiO₂ gate dielectrics has improved the speed of output drive current by shrinking of transistor area in front-end-process of integrated circuits. A higher number of transistors on chip resulting in faster speed and lower cost can be allowable by the scaling down and these fruitful achievements have been mainly made by the thinning thickness of one key component - Gate Dielectric - at Si based MOSFET (metal-oxide-semiconductor field effect transistor) devices. So far, SiO2 (silicon dioxide) gate dielectric having the excellent material and electrical properties such as good interface (i.e., Dit ~ 2x10¹⁰ eV⁻¹cm⁻²), low gate leakage current, higher dielectric breakdown immunity (≥10MV/cm) and excellent thermal stability at typical Si processing temperature has been popularly used as the leading gate oxide material. The next generation Si based MOSFETs will require more aggressive gate oxide scaling to meet the required specifications. Since high-k dielectrics provide the same capacitance with a thicker film, the leakage current reduction, therefore, less the standby power consumption is one of the huge advantages. Also, it is easier to fabricate during the process because the control of film thickness is still not in the critical range compared to the same leakage current characteristic of SiO₂ film. HfO₂ based gate dielectric is considered as the most promising candidate among materials being studied since it shows good characteristics with conventional Si technology and good device performance has been reported. However, it has still many problems like insufficient thermals stability on silicon such as low crystallization temperature, low k interfacial regrowth, charge trapping and so on. The integration of hafnium based high-k dielectric into CMOS technology is also limited by major issues such as degraded channel mobility and charge trapping. One approach to overcome these obstacles is using alternative substrate materials such as SiGe, GaAs, InGaAs, and InP to improve channel mobility. High electron mobility in the III-V materials has attracted significant attention for a possible application as a channel material in metal/oxide/semiconductor (MOS) transistors. One of the main challenges is that III-V MOSFETs generally lack thermodynamically stable insulators of high electrical quality, which would passivate the interface states at the dielectric/substrate interface and unpin the Fermi level. To address this issue, various dielectric, such as Si/SiO₂, Ge, SiGe, SiN and Al₂O₃, were considered as an interface passivation layer (IPL). Atomic Layer Deposited (ALD) Al₂O₃ has demonstrated superior IPL characteristics compared to the other candidates due to its high dielectric constant and interface quality. However, defect density in Al₂O₃ is still too high even as several cleaning methods such as NH₄OH, (NH₄)₂S and F treatment have been developed, which limits the performance of III-V MOSFETs. In the first part of this study, theoretical approaches to understand the motivation and requirements as an high-k gate dielectric or interfacial layer, and properties of ALD beryllium oxide (BeO) for Si and III-V MOS devices have been investigated. The second part of this study focuses on the precursor synthesis and fundamental material characterization of ALD BeO thin film using physical, optical and electrical analysis. Film properties such as self-cleaning reaction and oxygen diffusion barrier will be presented. At the third part, depletion mode transistor and self-aligned MOSFETs using ALD BeO on Si and InP high mobility substrates have been investigated. And as for the final part of this study, the density functional theory of Be(CH₃)₂ precursor, electromagnetics, and thermodynamics were investigated to understand the reaction mechanism and self-cleaning reaction, and to evaluate the gate dielectrics such as Al₂O₃, BeO, SiO₂, and HfO₂. / text

Ce manuscrit de thèse présente les recherches et les applications potentielles en tant que plate-forme (bio) capteur des couches minces conformes de ZnO et / ou Al2O3 / ZnO nanolaminates, déposées par dépôt de couche atomique (ALD) sur les différents substrats. Tout d'abord, une étude des propriétés optiques des films minces ZnO (20 et 50 nm) déposés par la technique ALD sur les grandes zones de nanofils de silicium ordonné (SiNW), réalisée en combinant la lithographie à la nanosphère et la gravure chimique à base de métal, a été réalisée. Ces méthodes ont permis la morphologie et le contrôle organisationnel des SiNW sur une grande surface. L'étude détaillée des propriétés structurales et optiques de l'hétérostructure SiNWs / ZnO à noyau-coquille a été réalisée en utilisant respectivement la spectroscopie XRD, SEM, de réflectance et de photoluminescence. L'intégration des tableaux SiNWs en tant que noyau et ZnO comme coque peut avoir un impact important sur le développement d'éléments de détection avec des propriétés améliorées. Dans les recherches ultérieures, des films ZnO formés par ALD en tant que plate-forme de biocapteur optique pour la détection des protéines de type A du virus Grapevine (antigènes GVA) ont été représentés. La détection de l'antigène GVA a été effectuée en utilisant les changements dans le comportement de la bande PL liée à la GVA. La sélectivité du biocapteur a été prouvée. La possibilité de détecter les antigènes GVA sans étiquettes supplémentaires a été démontrée. Ainsi, on a développé un biosensor à base de photoluminescence à base de photoluminescence libre pour les antigènes GVA. Une autre partie de notre étude est un contrôle spécifique de l'ancrage des protéines par le développement d'une surface multifonctionnelle avec une grande gamme de sphères de polystyrène (PSS), produite par la lithographie de nanosphère et bloquant davantage l'adsorption non spécifique des protéines à la surface du PSS par SAM de PEG. La microscopie d'épifluorescence a été utilisée pour confirmer qu'après l'immersion de l'échantillon sur la protéine cible (avidine et anti-avidine), ces dernières sont spécifiquement situées sur une sphère de polystyrène. Ces résultats sont significatifs pour l'exploration de dispositifs basés sur un nanoarray à grande échelle de sphères de PS et peuvent être utilisés pour la détection de protéines cibles ou simplement pour structurer une surface avec des protéines spécifiques. Notre recherche comprend également l'ajustement des propriétés structurelles et l'amélioration des propriétés électroniques et optiques des nanolaminés 1D PAN ZnO / Al2O3 conçus par dépôt de couche atomique (ALD) et électrospinning. Les propriétés structurelles et optiques de Al2O3 / ZnO déterminées à partir des analyses XPS, TEM, FTIR, XRD et PL. L'amélioration des propriétés électroniques et optiques permettrait l'application dans différents domaines de tels capteurs et biosensors. / This thesis manuscript presents the investigations and potential applications as a (bio)sensor platform of the conform thin layers of ZnO and/or Al2O3/ZnO nanolaminates, deposited by atomic layer deposition (ALD) on the various substrates. First, a study of the optical properties of ZnO thin films (20 and 50 nm) deposited by ALD technique on the large areas of ordered silicon nanowires (SiNWs), produced by combining nanosphere lithography and metal-assisted chemical etching, was performed. These methods allowed the morphology and the organization control of SiNWs on a large area. The detailed study of structural and optical properties of core-shell SiNWs/ZnO heterostructure was done by utilizing XRD, SEM, reflectance and photoluminescence spectroscopy, respectively. Integration of SiNWs arrays as core and ZnO as shell can have a strong impact on the development of sensing elements with improved properties. In the further investigations, ZnO films formed by ALD as an optical biosensor platform for the detection of Grapevine virus A-type proteins (GVA-antigens) were represented. The GVA-antigen detection was performed using the changes in the GVA related PL band behavior. The biosensor selectivity has been proved. The possibility to detect GVA-antigens without additional labels has been demonstrated. Thus, label free and sensitive photoluminescence based biosensor for GVA-antigens has been developed. Another part of our study is a specific control of protein anchoring by the development of multifunctional surface with large-scale array of polystyrene spheres (PSS), which produced by nanosphere lithography and further blocking the unspecific adsorption of protein on the surface of the PSS by PEG SAMs. The epifluorescence microscopy was used to confirm that after immersion of sample on target protein (avidin and anti-avidin) solution, the latter are specifically located on polystyrene sphere. These results are meaningful for exploration of devices based on large-scale nanoarray of PS spheres and can be used for detection of target proteins or simply to pattern a surface with specific proteins. Our research also includes the tuning of structural properties and the enhancement of electronic and optical properties of 1D PAN ZnO/Al2O3 nanolaminates designed by atomic layer deposition (ALD) and electrospinning. The structural and optical properties of Al2O3/ ZnO determined from the XPS, TEM, FTIR, XRD and PL analysis. The enhancement of electronic and optical properties would allow application in different fields such sensors and biosensors.

In this study, the characteristics of atomic layer deposited TiO2 films on silicon substrate were investigated. The physical and chemical properties were measured and surveyed. And an Al/ALD-TiO2/Si MOS structure was used for the electrical characterizations. For the electrical property improvements, we investigated the atomic layer deposited TiO2 films by the post-anneal treatments in nitrogen and oxygen ambient. Furthermore, the TiO2 films were passivated by fluorine ions to decrease the leakage current density that came from the liquid phase deposited SiO2 stacks. After the post-annealing and fluorine ions passivation treatments, the dielectric constant of atomic layer deposited TiO2 film was maintained and the leakage current density was improved.

In this study, the characteristics of atomic layer deposited TiO2 films on Gallium Arsenide substrate were investigated. The physical and chemical properties were measured and surveyed. And an Al/ALD-TiO2/GaAs MOS structure was used for the electrical characterizations. For the electrical property improvements, we investigated the atomic layer deposited TiO2 films by the (NH4)2Sx treatments for GaAs substrate. The leakage currents and the hysteresis loop flatband voltage shift can be improved for ALD-TiO2 films on S-GaAs. Furthermore, in order to resist the leakage current from the grain boundary of the polycrystalline TiO2 films, amorphous-like structure of TiO2 thinner films are investigated. The combination of sulfur passivation and amorphous-like structure thinner films is sufficient to improve the electrical properties effectively.

Due to the high electron mobility compared with Si, III-V compound semiconductors (GaAs) has been applied widely for high-speed devices. The titanium oxide (TiO2) has not only has high dielectric constant but has well lattice match with GaAs substrate. Therefore, the high-k material TiO2 was chosen to be the gate oxide in this study. The major problem of III-V compound semiconductors is known to have poor native oxide on it and leading to the Fermi level pinning at the interface between oxide and semiconductor. The C-V stretch-out phenomenon can be observed and the leakage current is high. The surface passivation of GaAs with (NH4)2Sx treatment (S-GaAs) can prevent it from oxidizing after cleaning and improve the interface properties. In order to passivate the grain boundary of polycrystalline ALD-TiO2 film and the interface state, the fluorine from liquid-phase- deposited SiO2 solution can achieve the goal effectively. In addition, the post-metallization annealing (PMA) is another efficiency way to improve the ALD-TiO2 film quality. The mechanism of PMA process is the reaction between the aluminum contact and hydroxyl groups existed on TiO2 film surface. Then the active hydrogen is produced to diffuse through the oxide and passivate the oxide traps.

Cette thèse se focalise sur les propriétés passivantes octroyées par des couches minces d’Al2O3 déposées par Atomic Layer Deposition (ALD) à partir de TMA et H2O pour les cellules photovoltaïques en silicium ayant des températures de fabrication inférieures à 400 °C. La première partie de ce travail de doctorat vise à identifier les mécanismes de formation des charges électrostatiques négatives présentes dans l’oxyde d’aluminium. Pour ce faire, les effets de l’illumination post-dépôt (à savoir le flux et l’énergie des photons), ainsi que la température du substrat ont été étudiés. Il a été constaté qu’au moins 70 % de ce qu’on appelle généralement les « charges fixes » sont en fait des charges piégées résultant de l’injection d’électrons du substrat de silicium dans l’oxyde d’aluminium. Par la suite, nous avons étudié l’influence des paramètres de dépôt de l’Al2O3 ainsi que l’impact des traitements post-dépôt sur le piégeage des charges et donc sur les performances passivantes qui en résulte au sein d’un empilement Al2O3/a-SiNX:H déposé sur du silicium cristallin de type p. Les liens entre l’épaisseur de l’Al2O3, la qualité et la durabilité de la passivation ont pu être établis. Le meilleur compromis s’est avéré être aux alentours 60 cycles ALD (~ 6 nm), permettant une durée de vie des porteurs de charges minoritaires allant jusqu’à 4500 μs. La deuxième partie de ce travail doctoral porte sur les mécanismes de dégradation de la passivation. La formation de cloques à l’interface c-Si/Al2O3 est le premier mécanisme de dégradation étudié. Grâce à la microscopie acoustique colorée, la dégradation de l’interface Al2O3/c-Si lors de l’épaississement de l’Al2O3 a été confirmée, mais également lors la réduction de sa température de dépôt, c’est-à-dire en augmentant sa teneur en hydrogène. Une dérive thermique pendant l’ALD (TD-ALD) a été utilisée pour résoudre ce problème de cloquage. L’augmentation continue de la température du substrat pendant le dépôt favorise la libération de l’hydrogène à partir de l’interface c-Si/Al2O3. Pour 60 cycles ALD, le TD-ALD a permis d’augmenter la durée de vie des porteurs de charges jusqu’à 5500 μs. Enfin, l’affaiblissement de la passivation par effet de champ résultant des charges positives dans la couche de protection a-SiNX:H a été mis en évidence par simulation numérique. Les propriétés du a-SiNX:H ont été expérimentalement optimisée grâce à une approche par plan d’expérience. Une nouvelle couche mince d’a-SiNX: H contenant 50 % de charges fixes positives en moins a permis d’obtenir une durée de vie des porteurs de charges de 8800 μs pour 60 cycles de TD-ALD, c’est-à-dire une vitesse de recombinaison de surface exceptionnelle basse de 0,8 cm.s-1. / This thesis focuses on the passivation properties provided by thin Al2O3 films grown by atomic layer deposition (ALD) from TMA and H2O for silicon solar cells having process temperatures lower than 400 °C. The first part of this doctoral work aims at identifying the formation mechanisms of negative electrostatic charges in aluminium oxide. Thus, the effects of post-deposition illumination (namely photon flux and photon energy), as well as substrate temperature were investigated. It was found that at least 70 % of what are generally named “fixed charges” are in fact trapped charges resulting from the injection of carriers from the silicon substrate into the aluminium oxide. From this result, we studied the influence of Al2O3 deposition parameters and post-deposition treatments on charge trapping and resulting passivation performances within an Al2O3/a-SiNX:H stack on p-type c-Si. The dependence of passivation performance (and stability) on Al2O3 thickness has been highlighted. Best compromise has been found to be around 60 ALD cycles (~6 nm), providing a lifetime up to 4500 µs. The second part of this PhD deals with the degradation mechanisms of passivation. Blistering at the c-Si/Al2O3 interface is the first studied degradation mechanism. Thanks to coloured picosecond acoustic microscopy, the Al2O3/c-Si adhesion has been confirmed to be reduced by Al2O3 thickening but also by the reduction of its deposition temperature, i.e. an increase of hydrogen content. A thermal drift during ALD (TD-ALD) has been used to solve this blistering issue. Gradual increase of the substrate temperature during the growth favours the release of hydrogen from the wafer/Al2O3 interface. For 60 ALD cycles, TD-ALD increased the lifetime up 5500 µs. Finally, the weakening of the electrostatic passivation arising from the positive charges in a-SiNX:H capping layer has been underlined by finite element simulations. The a-SiNX:H properties have been experimentally tuned thanks to a design of experiment approach. New a-SiNX:H capping containing 50 % less positive fixed charges resulted in a lifetime of 8800 µs for 60 TD-ALD cycles, i.e. an outstanding surface recombination velocity of 0.8 cm.s-1.

TiO2 films as electron collecting interlayers are important in determining the efficiency of organic photovoltaics (OPVs). Various methods of film deposition have been explored, and they revealed the tradeoff between pinhole free coverage (large shunt resistance) and small film thickness (small series resistance). It is hypothesized that atomic layer deposition (ALD) with its self-limiting nature and sub-nanometer level control would be able to circumvent this problem and provide TiO2 films of pinhole free coverage and small thickness. TiO2 films made by chemical vapor deposition (CVD) and ALD were investigated and compared. Conductive atomic force microscopy (CAFM) was used to characterize film morphology and conductivity. X-ray photoelectron spectroscopy (XPS) was utilized to analyze film composition and chemical state. Cyclic voltammetry (CV) was able to reveal the hole blocking capability of films. Finally, organic photovoltaic devices were made with different TiO2 films to reveal the relationship between device property and film characteristic. It is found that both CVD and ALD created TiO2 films with Ti4+ species containing oxygen from hydroxyl groups. They both showed conformal coverage of the electrode via CAFM and CV measurements, and clearly ALD method achieved this with a thinner film and smaller series resistance. This work provided the evidence of effective and surprising capabilities of electron harvesting and hole blocking of ultrathin ALD TiO2 films for OPVs.

Pour concevoir avec succès l'instrumentation nécessaire aux nouvelles technologies de fabrication avec une précision nanométrique, la méthodologie de conception doit prendre en compte de nombreux sujets différents liés à la chimie, à la physique, à la mécanique, à l'électronique et à l'automatisation, travaillant ensemble pour atteindre l'objectif souhaité. Dans cette thèse, cette méthodologie de conception a été mise en œuvre avec un grand nombre d’outils et d’approches permettant d’optimiser avec succès une méthode de nanofabrication appelée dépôt par couche atomique spatiale (SALD) afin de déposer des couches minces d’un matériau potentiellement utile en tant que composant du dispositifs à énergie solaire non-silicium, séparateurs d’eau photoélectrochimiques et composants électroniques transparents à couche mince, entre autres: oxyde cuivreux (Cu2O).En ce qui concerne la technologie de fabrication et la conception mécatronique, SALD est une technique de fabrication prometteuse qui permet la fabrication de films minces avec une précision nanométrique et avec la capacité de contrôler leurs propriétés mécaniques, électriques et cristallographiques. De plus, l'approche SALD utilisée dans cette thèse et dans le Laboratoire des matériaux et du génie physique (LMGP) fonctionne à l'air libre (sans chambre de dépôt) et constitue donc potentiellement une approche compatible avec l'industrie pour les films minces homogènes de grande surface fabrication avec un débit élevé. De plus, SALD peut être utilisé dans des conditions qui le rendent compatible avec les substrats flexibles et avec les approches de rouleau à rouleau (R2R). Enfin, SALD offre une flexibilité sur le processus de dépôt afin qu’il puisse être ajusté pour obtenir différentes propriétés sur les films fabriqués avec un minimum de modification de l’instrumentation.À l'aide de simulations CFD (Computational Fluid Dynamics), les phénomènes de la mécanique des fluides qui se produisent pendant le processus de dépôt dans le système SALD ont été analysés pour différentes configurations du réacteur. L'influence sur les propriétés du film a été étudiée et une validation avec des dépôts expérimentaux a été effectuée. Ensuite, en utilisant les connaissances et les directives obtenues avec les simulations CFD, et afin de réduire le coût et la complexité de la modification de certains composants mécaniques du système, un flux de travail comprenant la conception assistée par ordinateur (CAO) et la fabrication additive (également appelé impression 3D) impression) a été mis en place au LMGP pour la fabrication de l’un des composants principaux du système SALD à LMGP: la tête de dépôt. Ici, c'est la première fois qu'une telle technique de fabrication innovante est appliquée aux processus de nanofabrication en couches minces, offrant de nombreuses applications potentielles dans le domaine. Dans cette thèse, un tel flux de travail est présenté et expliqué, ainsi que les directives apprises et les limitations découvertes également présentées.Enfin, couches minces de Cu2O ont été déposé avec succès avec la méthode SALD. Le Cu2O est l’un des rares matériaux aux propriétés électroniques prometteuses en tant que semi-conducteur transparent de type p. Ici, les films de Cu2O fabriqués utilisant le système SALD à LMGP sont rapportés et leur conductivité de type p et leur cristallographie sont analysées.Les résultats de ces travaux fournissent des directives initiales pour la conception industrielle d’un système de fabrication à haut débit basé sur la technologie SALD, dans lequel la conception de ses composants est optimisée pour chaque matériau souhaité. Cette approche de conception rend également ce travail utile pour augmenter la quantité de matériaux compatibles avec le SALD, ainsi que pour développer davantage la méthodologie SALD dans des processus de fabrication innovants de matériaux et de dispositifs. / To successfully design the instrumentation needed for new manufacturing technologies with nanoscale precision, the design methodology must take into account many different topics related to chemistry, physics, mechanics, electronics and automation, working together to achieve the desired goal. In this thesis, this design methodology has been implemented with a large number of tools and approaches to successfully optimize a nanofabrication method called spatial atomic layer deposition (SALD) in order to deposit thin films. a potentially useful material as a component of non-silicon solar energy devices, photoelectrochemical water separators and transparent thin-film electronic components, among others: cuprous oxide (Cu2O).With respect to manufacturing technology and mechatronics design, SALD is a promising manufacturing technique that enables the fabrication of thin films with nanoscale precision and the ability to control their mechanical, electrical and crystallographic properties. In addition, the SALD approach used in this thesis and in the Laboratoire des Matèriaux et du Génie Physique(LMGP) works in the open air (without a repository) and is therefore potentially an industry-compatible approach to film Thin homogeneous high-area manufacturing with high throughput. In addition, SALD can be used under conditions that make it compatible with flexible substrates and roll-to-roll approaches (R2R). Finally, SALD offers flexibility on the deposit process so that it can be adjusted to obtain different properties on films manufactured with a minimum of instrumentation modification.Using CFD (Computational Fluid Dynamics) simulations, the fluid mechanics phenomena that occur during the deposition process in the SALD system were analyzed for different reactor configurations. The influence on the properties of the film was studied and a validation with experimental deposits was carried out. Then, using the knowledge and guidance obtained with CFD simulations, and to reduce the cost and complexity of modifying certain mechanical components of the system, a workflow that includes computer-aided design (CAD) and manufacturing additive (also called 3D printing) printing) was set up at the LMGP for the manufacture of one of the main components of the LMGP SALD system: the deposit head. Here, it is the first time that such an innovative manufacturing technique has been applied to thin-film nanofabrication processes, offering many potential applications in the field. In this thesis, such a workflow is presented and explained, along with learned guidelines and discovered limitations also presented.Finally, thin layers of Cu2O have been successfully deposited with the SALD method. Cu2O is one of the few materials with promising electronic properties as a p-type transparent semiconductor. Here, Cu2O films made using the LMGP SALD system are reported and their p-type conductivity and crystallography are analyzed.The results of this work provide initial guidance for the industrial design of a high throughput manufacturing system based on SALD technology optimized for each desired material. This design approach also makes this work useful for increasing the amount of SALD compatible materials, as well as for further developing the SALD methodology in innovative materials and device manufacturing processes.

Electrolessly deposited CoWP capping layers have been demonstrated to effectively reduce electromigration of Cu at the interconnect/dielectric-barrier cap interface while reducing resistivity relative to SiCN. However, as device dimensions scale, the need for alternative methods for the selective deposition of sub-5 nm, ultrathin, conformal Co capping layers is apparent. To develop methods for area-selective atomic layer deposition (AS-ALD) of Co caps for next-generation Cu interconnects, the ALD behavior of bis(N-tert-butyl-N’-ethylpropionamidinato) cobalt(II) (CoAMD) is evaluated on Cu, SiO₂, and a porous low-k ( ~2.6) dielectric, CDO. The first and second ALD half reactions of CoAMD on the respective substrates is evaluated with H₂ coreactant by adsorbing the precursor on the substrates under ALD cycling conditions at 265 °C with and without coreactant exposure. The adsorption studies indicate that CoAMD preferentially deposits most on Cu and least on CDO. Further, CoAMD, like other amidinate precursors, readily dissociates on the Cu transition metal surface but the ultimate per-cycle coverage is self-limited by the slow desorption of amidinate ligands and fragments from the Cu surface. Co films deposited by ALD from CoAMD on Cu at 265 °C indicate that Co burrows into the lower energy Cu surface as the film grows in order to reduce the free surface energy. The Cu remains as a surfactant-like layer on the topmost Co surface up to film thicknesses of at least 16 nm. Moreover, considerable intermixing at the Co/Cu interface and Cu concentration several nm into the Co films are observed indicating high surface mobility of the two materials and Cu diffusion at polycrystalline Co grain boundaries. Finally, employing low-tempurature ALD and selectively passivating the dielectric surfaces with OH targeting passivants leads to enhanced selectivity of CoAMD for deposition on Cu versus SiO₂ and CDO. Depositing Co from CoAMD on Cu and CDO at 165 °C after 500 kTorr-s exposure to trimethylchlorosilane at 50 °C leads to a 30:1 preference for Co accumulation on Cu, a twelve times improvement compared to deposition on cleaned Cu and CDO at 265 °C. / text

In this study, the thin titanium oxide (TiO2) film deposited on InP substrate was prepared by atomic layer deposition (ALD), which was used as gate oxide of InP Schottky barrier MOSFET. First, aluminum oxide (Al2O3) by ALD can be used as improvement in oxide of TiO2. Al2O3 of ALD has self-cleaning which can improve interface between oxide and substrate, the leakage current densities can reach 3.1 ¡Ñ 10-9 and 3.3 ¡Ñ 10-7 A/cm2. The Schottky barrier height(£XBp) of Al/InP with (NH4)2S treatment is 0.968 eV, which is higher than that of Al/InP without (NH4)2S treatment (0.806eV). The (NH4)2S solution is a moderate etchant to reduce surface oxides on InP. Therefore, Schottky barrier will not be influenced by Fermi level pinning. The electrical characteristics of Schottky barrier MOSFET with TiO2 as gate oxide were measured in this report. The drain current is 1.73£gA. The drain current increases rapidly when drain voltage is over 1V, it indicates that breakdown field of TiO2 thin film is not high enough. Due to advantages of ALD-Al2O3, such as self-cleaning ability and high breakdown field, the TiO2/Al2O3 prepared by ALD structure was used to improve the problem mentioned above. The electrical characteristics are much improved compared with a single TiO2 film, and drain current can reach 1.37 £gA. The rapid increase of drain current with the increased drain voltage is not observed. The transconductance and mobility are 4.45 ¡Ñ 10-7 S/£gm and 202.3 mm2/V-s, respectively, and a good sub-threshold behavior is obtained. Compared with other researches, we can find that Schottky barrier in on-state is higher than that of silicide sample. It indicates the InP Schottky barrier MOSFET characteristics are limited by high Schottky barrier.