Search query: -Al2O3 layer amorphous-phase structure

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abstract: Metal insulator semiconductor (MIS) structures were fabricated on n type variband HgCdTe with Al2O3 deposited by plasma enhanced ALD. Early stages of the deposition process performed at 120 degC were studied by means of XPS for the first time. Partial decomposition and conversion of HgCdTe native oxide presented on the surface were observed as well as mercury atoms out diffusion from the near surface region. The width of alumina band gap and the offsets of Al2O3/HgCdTe bands were determined. Capacitance voltage characteristics reveal a negative fixed charge with the density of ~1 x 1012 cm 2 and wide hysteresis depending on the voltage sweep range. An additional intermediate layer lowering an apparent permittivity value of the MIS insulator layer is found. By varying the thickness of the insulator of the samples, the permittivity of Al2O3 was extracted to be 7.6. The estimated Al2O3 properties correspond to the oxygen deficient amorphous phase of alumina.
author_names: Evgeny R Zakirov

Valeriy G Kesler

G Yu Sidorov

Igor P Prosvirin

Anton K Gutakovsky

V I Vdovin
title: XPS investigation of the ALD Al2O3/HgCdTe heterointerface
venue: Semiconductor Science and Technology
year: 2019

abstract: Abstract During the first stages of Atomic Layer Deposition (ALD) of Al2O3 on silicon (Si) the substrate nature affects the surface chemistry, leading to an initial island growth mode. Furthermore, an interfacial zone develops between the Si surface and the dielectric, thus damaging the physical properties of the deposited structure. In this work, these two main shortcomings are investigated for the ALD of Al2O3 films on Si from TMA and H2O. The film and the interfacial zone are characterized by a complete range of techniques, including XRR, TEM, XPS, EDX and ToF SIMS. In parallel, a computational model is developed to study the initial nucleation and growth steps of the film. An induction period is experimentally evidenced and numerically reproduced, together with the island growth and coalescence phenomena. The chemical composition of the (Al, O, Si) interfacial layer is precisely analyzed to get insight in the mechanisms of its formation. We show that Si oxidation occurs during the island growth, catalyzed by the presence of Al, while it is also fed by species interdiffusion through the ALD film.
author_names: Georgios Gakis

Constantin Vahlas

Hugues Vergnes

Sandrine Dourdain

Y Tison

Herve Martinez

Jerome Bour

David S Ruch

Andreas G Boudouvis

Brigitte Caussat

Emmanuel Scheid
title: Investigation of the initial deposition steps and the interfacial layer of Atomic Layer Deposited (ALD) Al2O3 on Si
venue: Applied Surface Science
year: 2019

abstract: We have characterized the interface states of Al2O3/GaN and Al2O3/AlGaN/GaN structures prepared by atomic layer deposition using the conventional and photo assisted capacitance voltage (C V) measurements. In order to control the interface states, an N2O radical treatment was applied to the GaN and AlGaN surfaces prior to the deposition of the Al2O3 layer. We observed good C V behavior and a relatively low density of interface states for the N2O radical treated Al2O3/GaN structure. To estimate the state density distributions at the Al2O3/AlGaN interface, we applied the photo assisted C V measurement to the Al2O3/AlGaN/GaN heterostructures. The present Al2O3/AlGaN structre showed higher interface state densities than the Al2O3/GaN structure. However, we found that the N2O radical treatment is effective in reducing the density of interface states at the Al2O3/GaN and Al2O3/AlGaN systems (c) 2012 WILEY VCH Verlag GmbH Co. KGaA, Weinheim)
author_names: Yuji Hori

Chihoko Mizue

Tamotsu Hashizume
title: Interface state characterization of ALD Al2O3/GaN and ALD Al2O3/AlGaN/GaN structures
year: 2012

abstract: The effects of fabrication processes on the electrical properties of Al2O3/GaN structures prepared by atomic layer deposition were investigated. The annealing process at 800 degC for the formation of ohmic electrodes brought a large number of microcrystallization regions into the Al2O3 layer, causing a marked leakage in the current voltage characteristics of the Al2O3/GaN structure. The "ohmic first" process with a SiN protection layer was thus applied to the GaN surface. In this process, the amorphous phase in the atomic configuration of Al2O3 was maintained, leading to the sufficient suppression of leakage current at the Al2O3/GaN interface. In addition, the Al2O3/GaN structures showed good capacitance voltage characteristics, resulting in low interface state densities of less than 1x1012 cm 2 eV 1.
author_names: Yuji Hori

Chihoko Mizue

Tamotsu Hashizume
title: Process Conditions for Improvement of Electrical Properties of Al2O3/n GaN Structures Prepared by Atomic Layer Deposition
year: 2010

abstract: We performed interfacial electric and electronic studies of both in situ and ex situ atomic layer deposited (ALD) Al2O3 films on InGaAs. Self aligned inversion channel metal oxide semiconductor field effect transistors (MOSFETs) with a 1 mm gate length (Lg) from the in situ sample have extrinsic drain currents (Id) of 1.8 mA/mm, transconductances (Gm) of 0.98 mS/mm, and an effective mobility (meff) of 1250 cm2/V s. MOSFETs that employ ex situ ALD Al2O3 have an Id of 0.56 mA/mm, Gm of 0.28 mS/mm, and meff of 410 cm2/V s. Synchrotron radiation photoemission reveals no AsOx residue at the Al2O3/InGaAs interface using the in situ approach, whereas some AsOx residue is detected using the ex situ method.
author_names: Minghwei Hong

H W Wan

K Y Lin

Yu Cheng Chang

Mei-Hsin Chen

Yung-Hsiang Lin

T D Lin

Tun Wen Pi

Jueinai Kwo
title: Perfecting the Al2O3/In0.53Ga0.47As interfacial electronic structure in pushing metal oxide semiconductor field effect transistor device limits using in situ atomic layer deposition
year: 2017

abstract: This study compares the physical, chemical and electrical properties of Al2O3 thin films deposited on gallium polar c and nonpolar m plane GaN substrates by atomic layer deposition (ALD) Correlations were sought between the film's structure, composition, and electrical properties. The thickness of the Al2O3 films was 19.2 nm as determined from a Si witness sample by spectroscopic ellipsometry. The gate dielectric was slightly aluminum rich (Al:O=1:1.3) as measured from X ray photoelectron spectroscopy (XPS) depth profile, and the oxide semiconductor interface carbon concentration was lower on c plane GaN. The oxide's surface morphology was similar on both substrates, but was smoothest on c plane GaN as determined by atomic force microscopy (AFM) Circular capacitors (50 300 mm diameter) with Ni/Au (20/100 nm) metal contacts on top of the oxide were created by standard photolithography and e beam evaporation methods to form metal oxide semiconductor capacitors (MOSCAPs) The alumina deposited on c plane GaN showed less hysteresis (0.15 V) than on m plane GaN (0.24 V) in capacitance voltage (CV) characteristics, consistent with its better quality of this dielectric as evidenced by negligible carbon contamination and smooth oxide surface. These results demonstrate the promising potential of ALD Al2O3 on c plane GaN, but further optimization of ALD is required to realize the best properties of Al2O3 on m plane GaN. (c) 2014 WILEY VCH Verlag GmbH Co. KGaA, Weinheim)
author_names: Daming Wei

Tashfin Hossain

Neeraj Nepal

Nelson Y Garces

Jennifer K Hite

Harry M Meyer

Charles R Eddy

James H Edgar
title: Comparison of the physical, chemical and electrical properties of ALD Al2O3 on c and m plane GaN
year: 2014

abstract: Data on X ray diffraction in lanthanum diphthalocyanine pyrolysates synthesized at temperatures of 800 1800degS demonstrate the formation of an amorphous carbon phase with embedded lanthanum atoms. Low temperature pyrolysis (800 900degS) creates layered carbon structures. Due to annealing at 1000degS, carbon integrates into globules whose number of atoms is m 100. Such structures with gyration radii of Rg 0.4 0.5 nm on the order of the precursor molecule size are synthesized in the temperature range of 1000 1800degS, and are stable in terms of size and mass. In this case, their density approaches that of graphite.
author_names: Vasiliy T Lebedev

A E Sovestnov

Vladimir I Tikhonov

Y P Chernenkov
title: Structure of the amorphous phase of pyrolisates of lanthanum diphthalocyanine according to X ray scattering data
venue: Journal of Surface Investigation: X ray, Synchrotron and Neutron Techniques
year: 2017

abstract: The characteristics of the oxide layer deposited by microarc oxidation (MAO) on Al Si alloys in a silicate alkaline electrolyte are studied. The thermal conductivity of the layer at 50 120degC is determined using a special facility by the method of stationary heat flow. The thickness, the porosity, the elemental composition, the content of the amorphous phase, and the size of the crystallites in the oxide layer are determined. The results obtained are analyzed and the conditions for the lowest thermal conductivity of the oxide layer are determined.
author_names: Natalia Y Dudareva

Pavel V Ivashin

R F Gallyamova

A Ya Tverdokhlebov

Mikhail M Krishtal
title: Structure and Thermophysical Properties of Oxide Layer Formed by Microarc Oxidation on AK12D Al Si Alloy
venue: Metal Science and Heat Treatment
year: 2021

abstract: Atomic layer deposition (ALD) of Al2O3 was used to prepare metal oxide semiconductor (MOS) devices on two different_AlGaN/GaN heterostructures, with and without a thin GaN cap layer. Their trapping effects were evaluated by the frequency dependent conductance measurement. The trap state density decreased sharply from ~1x1012 cm 2 eV 1 at the energy of 0.27 eV to ~3x1010 cm 2 eV 1 at 0.45 eV. The low trap state density and exactly exponential dependence of the trap state time constant on the gate voltage show a good quality of the gate oxide. The trap state density in the structure with a GaN cap is about 2 3 times lower than that in the structure without a cap, which might be due to the different Al2O3/GaN and Al2O3/AlGaN interface properties. The trap state density in the structures investigated is lower than those reported for the devices with the metal organic chemical vapor deposition and Al oxidized Al2O3 gate oxide. This shows an importance of the ALD technique for the preparation of high performanc.
author_names: Dagmar Gregusova

Roman Stoklas

Chihoko Mizue

Yuji Hori

Jozef Novak

Tamotsu Hashizume

Peter Kordos
title: Trap states in AlGaN/GaN metal oxide semiconductor structures with Al2O3 prepared by atomic layer deposition
year: 2010

abstract: Patterned layers of Al2O3 prepared by atomic layer deposition (ALD) are used to produce structures of alternating polarity (c plane orientation) of GaN on Ga polar GaN epilayers. Annealing prior to epitaxial growth allows the amorphous ALD layers to attain sufficient crystallinity, which enables N polar GaN growth over the annealed ALD Al2O3 and Ga polar growth over the bare substrate. Transmission electron microscopy and electron channeling contrast imaging were carried out to characterize the structural nature of the material and confirm crystallinity. ALD Al2O3 may be suitable for fabricating novel variable polarity devices, particularly where growth on native, Ga polar GaN substrates is beneficial.
author_names: Jennifer K Hite

Nelson Y Garces

Ramasis Goswami

Michael A Mastro

Fritz J Kub

Charles R Eddy
title: Selective switching of GaN polarity on Ga polar GaN using atomic layer deposited Al2O3
year: 2014