Stress and Microstructure Evolution in Compositionally Graded Al1-xGaxN Buffer Layers for GaN Growth on Si

2005 ◽  
Vol 892 ◽  
Author(s):  
Xiaojun Weng ◽  
Srinivasan Raghavan ◽  
Elizabeth C Dickey ◽  
Joan M Redwing
Keyword(s):  
Buffer Layer ◽  
Compressive Stress ◽  
Microstructure Evolution ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Cross Sectional ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Annihilation

AbstractWe have studied the evolution of stress and microstructure of compositionally graded Al1-xGaxN (0 ≤ x ≤1) buffer layers on (111) Si substrates with varying thicknesses. In-situ stress measurements reveal a tensile-to-compressive stress transition that occurs near the half-thickness in each buffer layer. Cross-sectional transmission electron microscopy (TEM) shows a significant reduction in threading dislocation (TD) density in the top half of the buffer layer, suggesting that the compressive stress enhances the threading dislocation annihilation. The composition of the buffer layers varies linearly with thickness, as determined by X-ray energy dispersive spectrometry (XEDS). The composition grading-induced compressive stress offsets the tensile stress introduced by microstructure evolution, thus yielding a tensile-to-compressive stress transition at x ≈ 0.5.

A Novel Approach for The Production of Low Dislocation Relaxed Sige Material.

1993 ◽  
Vol 319 ◽  
Author(s):  
A.R. Powell ◽  
S.S. Iyer ◽  
F.K. Legoues
Keyword(s):  
Sige Layer ◽  
Silicon On Insulator ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Tem Analysis ◽  
Cross Sectional ◽  
Novel Approach ◽  
Transmission Electron ◽  
Silicon Thickness ◽  
Buffer Structure

AbstractIn this growth process a new strain relief mechanism operates, whereby the SiGe epitaxial layer relaxes without the generation of threading dislocations within the SiGe layer. This is achieved by depositing SiGe on an ultrathin Silicon On Insulator, SOl, substrate with a superficial silicon thickness less than the SiGe layer thickness. Initially, the thin Si layer is put under tension due to an equalization of the strain between the Si and SiGe layers. Thereafter, the strain created in the thin Si layer relaxes by plastic deformation. Since the dislocations are formed and glide in the thin Si layer, no threading dislocation is ever introduced into the upper SiGe material, which appeared dislocation free to the limit of the cross sectional Transmission Electron Microscopy (TEM) analysis. We thus have a method for producing very low dislocation, relaxed SiGe films with the additional benefit of an SO substrate. This buffer structure is significantly less than a micrometer in thickness and offers distinct advantages over the thick SiGe buffer layers presently in use.

Atomic Force Microscopy Study of GaN-Buffer Layers on SiC(0001) By MOCVD

1996 ◽  
Vol 423 ◽  
Author(s):  
Dongsup Lim ◽  
Dongjin Byun ◽  
Gyeungho Kim ◽  
Ok-Hyun Nam ◽  
In-Hoon Choi ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Microscopy Study ◽  
Growth Conditions ◽  
Interfacial Free Energy ◽  
Buffer Layers ◽  
Optimum Growth ◽  
Cross Sectional ◽  
Atomic Force ◽  
Transmission Electron ◽  
Gan Buffer Layer

AbstractBuffer layers promote lateral growth of films due to a decrease in interfacial free energy between the film and substrate, and large 2-dimensional nucleation. Smooth surfaces of thebuffer layers are desired. Optimum conditions for GaN-buffer growth on the vicinal surface of 6H-SiC(0001) were determined by atomic force microscope (AFM). AFM analysis of the GaN nucleation layers led to an optimum growth conditions of the GaN-buffer layer which was confirmed by cross-sectional transmission electron microscopy, Hall measurements and photoluminescence spectra. Optimum growth conditions for GaN-buffer layer on SiC(0001) was determined to be 1 minute growing at 550°C.

MBE Growth of GaAs on Si (100)

1987 ◽  
Vol 91 ◽  
Author(s):  
J. S. Ahearn ◽  
P. Uppal
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Tem Analysis ◽  
Cross Sectional ◽  
Mbe Growth ◽  
Si Substrates ◽  
Gaas On Si ◽  
Linear Defects ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Annihilation

ABSTRACTMolecular beam epitaxy (MBE) growth of GaAs on Si was investigated for three Si substrate orientations: exact (100), 4° off (100) towards (011), and 4° off towards (010). Cross-sectional transmission electron microscopy (X-TEM) analysis indicated a high dislocation density at the GaAs-Si interface that decreased away from the interface. Changing the orientation significantly affected the dislocation arrangement in the films.In the exact (100) case, dislocations from different glide systems formed pyramids, and dislocation annihilation resulted in linear defects propagating to the bottom of pits on the GaAs surface. On Si substrates oriented 4° off of (100), dislocation pyramids were not observed which we attribute to the different stresses acting on different glide systems. Planar TEM sections indicated that the dislocation densities at th surfaces of the 2-μm-thick films were 8 × 108 /cm2 for exact (100), 3.4 × 108/cm2 for 4° off (100) towards (010), and 1.6 × 108/cm2 for 4° off towards (011) orientations. When etching was used to evaluate anti-phase domain (APD) density, the exact (100) and off (100) orientations toward (010) showed APD's in some areas; off (100) toward (011) orientations were apparently APD-free. Results of photoluminescence (PL) spectroscopy of each of the wafers showed marked differences in peak intensities for the different orientations. Secondary ion mass spectrometry (SIMS) showed that roughly 1/4 of a monolayer of Si was incorporated in the GaAs, mostly concentrated in the first 250 nm near the GaAs-Si interface.

Interfacial Strain Reliefs in Epitaxial YBa2Cu3O7–δ Thin Films Grown on SrTiO3 Buffered MGO Substrates

1997 ◽  
Vol 505 ◽  
Author(s):  
Xingtian Cui ◽  
Q. Y Chen ◽  
Yongxiang Guo ◽  
W. K. Chu
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
Rutherford Backscattering Spectrometry ◽  
Epitaxial Thin Films ◽  
Cross Sectional ◽  
Ybco Films ◽  
Ion Channeling ◽  
Transmission Electron ◽  
Edge Dislocations

ABSTRACTHigh quality YBa2Cu3O7–δ, (YBCO) epitaxial thin films grown on MgO substrate with a strainrelieved SrTiO3 (STO) buffer layer have been investigated by Rutherford backscattering spectrometry (RBS), ion channeling and high resolution cross sectional transmission electron microscopy (XTEM). The in-situ growth of STO buffer layer along with the YBCO films was carried out by pulsed laser ablation. In this work, minimum yield of channeling measurements have shown that a very thin STO buffer layer is sufficient to grow highly crystalline YBCO thin films on MgO substrates. TEM studies showed that the STO layers were strain-relieved by an array of periodic edge dislocations. The YBCO films on STO buffer, as in those grown directly on an STO substrate, evolved from a strained layer to a largely dislocation free area.

In situ transmission electron microscopy investigation of threading dislocation motion in passivated thin aluminum films

1999 ◽  
Vol 14 (12) ◽  
pp. 4673-4676 ◽  
Author(s):  
R-M. Keller-Flaig ◽  
M. Legros ◽  
W. Sigle ◽  
A. Gouldstone ◽  
K. J. Hemker ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Motion ◽  
Aluminum Film ◽  
Threading Dislocation ◽  
Cross Sectional ◽  
Aluminum Films ◽  
Transmission Electron ◽  
Microscopy Investigation

In situ transmission electron microscopy (TEM) was performed to study dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between dislocations and interfaces, the movement of threading dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of threading dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.

Effect of Si Doping on The Structure of Gan

1996 ◽  
Vol 423 ◽  
Author(s):  
Zuzanna Liliental-Weber ◽  
S. Ruvimov ◽  
T. Suski ◽  
J. W. Ager ◽  
W. Swider ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Dopant Concentration ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Silicon Doping ◽  
Defect Reduction ◽  
Si Doping ◽  
Transmission Electron ◽  
Metal Organic

AbstractThe influence of Si doping on the structure of GaN grown by metal-organic chemicalvapor deposition (MOCVD) has been studied using transmission electron microscopy (TEM), x-ray diffraction and Raman spectroscopy. Undoped and low Si doped samples were compared with samples of increased dopant concentration. In addition, defect reduction due to different buffer layers (AIN and GaN) is discussed. Silicon doping improves surface morphology and influences threading dislocation arrangement. High doping leads to a more random distribution of dislocations. Based on this study it appears (for the same dopant concentration) that an AIN buffer layer can significantly reduce the number of threading dislocations, leaving the samples more strained. However, no significant reduction of threading dislocations could be observed in the samples with GaN buffer layer. These samples are the least strained.

Microstructure Evolution During Solid-State Reactions in Polycrystalline Nb/Al and Ti/Ai Multilayer Thin-Films

1999 ◽  
Vol 562 ◽  
Author(s):  
G. Lucadamo ◽  
K. Barmak ◽  
D. T. Carpenter ◽  
C. Lavoie ◽  
C. Cabral ◽  
...  
Keyword(s):  
Thin Films ◽  
Microstructure Evolution ◽  
Metastable Phase ◽  
Scanning Transmission Electron Microscope ◽  
Grain Structure ◽  
Solid State Reactions ◽  
Multilayer Thin Films ◽  
Cross Sectional ◽  
Transmission Electron

ABSTRACTThe microstructural changes that occur during the reaction of sputter-deposited Nb/Al and Ti/Al multilayer thin-films with bilayer thicknesses ranging from 10 nm to 333 nm have been studied. The films were deposited with an overall stoichiometry of XAl3 (X = Nb,Ti) and subsequently annealed to different stages of the reaction in a differential scanning calorimeter (DSC). Data obtained from cross-sectional transmission electron microscopy (XTEM), and in situ synchrotron X-ray diffraction (XRD) experiments have provided evidence for a two-stage reaction mechanism for the formation of NbAl3. Microscopy results from a film with a bilayer period of 333 nm showed a microstructure that was consistent with two-dimensional growth in the plane of the interface. A uniform, 10 nm thick continuous layer of the product phase was formed followed by growth normal to the interface that initially consisted of larger, faceted grains. By the end of the reaction, an equiaxed NbAl3 grain structure was observed. High resolution elemental mapping using a scanning transmission electron microscope (STEM) revealed penetration of Nb into the Al layer and enhanced growth in regions where Al grain boundaries intersected the interface. Characterization of microstructure evolution in the Ti/Al system was complicated by the formation of two metastable structures consisting of cubic Ll2 followed by tetragonal DO23, and finally the equilibrium, tetragonal DO22 structure. However, the metastable phase transition temperatures were clearly isolated using the in situ XRD technique.

Xps Analysis of Y-Ba-Cu-O and Zr-O Thin Films and Interfaces with Silicon Substrates

1989 ◽  
Vol 169 ◽  
Author(s):  
D.B. Fenner ◽  
A.M. Viano ◽  
G.A.N. Connell ◽  
J.B. Boyce ◽  
D.K. Fork ◽  
...  
Keyword(s):  
Thin Films ◽  
Buffer Layers ◽  
Silicon Substrates ◽  
Cross Sectional ◽  
Si Substrates ◽  
Bulk Ybco ◽  
Transmission Electron ◽  
Oxide Etching ◽  
Lattice Images ◽  
Zirconia Films

AbstractThin films of Y1Ba2Cu3Ox,ZrO2, and yttria-stabilized zirconia (YSZ) have been deposited on Si(100) by the UV-laser ablation technique, and characterized by several techniques including x-ray photoemission spectroscopy (XPS) and cross-sectional transmission electron microscopy (XTEM). Si substrates were prepared by several techniques including thermal oxidation, and oxide etching and passivation by hydrogen termination. Certain of these YBCO films (= 250 nm thick) deposited on YSZ buffer layers have excellent superconducting properties. Other YBCO and zirconia films, deposited to 2-5 nm thickness and transferred under dry N2 into UHV, allowed XPS evaluation of the thermal and chemical stability of the interfaces and nearby regions. 2-nm films of YBCO on 15-nm films of SiO2/Si, deposited at 550–670 °C, showed Cu 2p core-level XPS lines similar to those of bulk YBCO (i.e., Cu II) but with two components due to reactions. The Si 2p line showed formation of silica on the YBCO surface at 670 °C and of silicate at 550 °C. XTEM lattice images showed that use of H-terminated Si produced superior interfaces with the zirconia films.

Evaluation of Anti-Phase-Boundaries in GaAs/Si Heterostructures by Transmission Electron Microscopy

1989 ◽  
Vol 148 ◽  
Author(s):  
O. Ueda ◽  
T. Soga ◽  
T. Jimbo ◽  
M. Umeno
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Three Dimensional ◽  
Buffer Layers ◽  
Phase Boundaries ◽  
Cross Sectional ◽  
Si Substrates ◽  
Transmission Electron ◽  
Strained Layer Superlattices ◽  
And Behavior

ABSTRACTThe nature and behavior of anti-phase-boundaries in GaAs/Si heterostructures using GaP, GaP/GaAsP and GaAsP/GaAs strained layer superlattices as intermediate buffer layers, have been investigated by transmission electron microscopy. It has been found that anti-phasedomains are very complicated three dimensional polygons consisting of several sub-boundaries in different orientations. Self-annihilation of anti-phase-domains during crystal growth of GaAs on (001)just or (001)2°off Si substrates is directly observed for the first time through planview and cross-sectional observations. Based on these findings, a mechanism of annihilation of these domains is proposed.

In-Situ Study of NiO Growth on Textured Nickel Tape Using Environmental Scanning Electron Microscope (ESEM) and Hot Stage

2001 ◽  
Vol 7 (S2) ◽  
pp. 1276-1277
Author(s):  
Y. Akin ◽  
R.E. Goddard ◽  
W. Sigmund ◽  
Y.S. Hascicek
Keyword(s):  
Buffer Layer ◽  
Lattice Mismatch ◽  
Sol Gel ◽  
Surface Oxidation ◽  
Dip Coating ◽  
Buffer Layers ◽  
Superconducting Film ◽  
Environmental Scanning ◽  
Cold Rolling And Annealing

Deposition of highly textured ReBa2Cu3O7−δ (RBCO) films on metallic substrates requires a buffer layer to prevent chemical reactions, reduce lattice mismatch between metallic substrate and superconducting film layer, and to prevent diffusion of metal atoms into the superconductor film. Nickel tapes are bi-axially textured by cold rolling and annealing at appropriate temperature (RABiTS) for epitaxial growth of YBa2Cu3O7−δ (YBCO) films. As buffer layers, several oxide thin films and then YBCO were coated on bi-axially textured nickel tapes by dip coating sol-gel process. Biaxially oriented NiO on the cube-textured nickel tape by a process named Surface-Oxidation- Epitaxy (SEO) has been introduced as an alternative buffer layer. in this work we have studied in situ growth of nickel oxide by ESEM and hot stage.Representative cold rolled nickel tape (99.999%) was annealed in an electric furnace under 4% hydrogen-96% argon gas mixture at 1050°C to get bi-axially textured nickel tape.

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