Dependence of the Residual Strain in GaN on the AlN Buffer Layer Annealing Parameters

1997 ◽  
Vol 468 ◽  
Author(s):  
Y.-M. Le Vaillant ◽  
S. Ciur ◽  
A. Andenet ◽  
O. Briot ◽  
B. Gil ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Annealing Time ◽  
Residual Strain ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Amorphous State ◽  
Lattice Parameter ◽  
Optical Quality ◽  
Buffer Layers ◽  
Aln Buffer

ABSTRACTThe problem of residual strain in GaN epilayers is currently the attention of many studies, since it affects the optical and electrical properties of the epilayers. In order to discuss the origin of this residual strain, we have grown a series of GaN epilayers onto AlN buffer layers, sapphire (0001) being used as substrate. The buffer layer is usually deposited in an amorphous state and is recrystallized by a thermal annealing. Here we have made a systematic study of the buffer recrystallization by changing the annealing temperature and the annealing time. The surface morphology is probed using Atomic Force Microscopy (AFM). The lattice parameter c is carried out from accurate x-ray diffraction measurements. The GaN layers were studied by low temperature photoluminescence and reflectivity. The amount of residual strain is calibrated from the position of the A exciton and the optical quality of the layers is assessed from the photoluminescence linewidths. The longer the annealing time the better the strain relaxation in AlN buffer layers and the higher the lattice mismatch with GaN overlayers.

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.

scholarly journals Improved Performance of GaN-Based Light-Emitting Diodes Grown on Si (111) Substrates with NH3 Growth Interruption

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 399
Author(s):  
Sang-Jo Kim ◽  
Semi Oh ◽  
Kwang-Jae Lee ◽  
Sohyeon Kim ◽  
Kyoung-Kook Kim
Keyword(s):  
Buffer Layer ◽  
Light Emitting Diodes ◽  
Defect Density ◽  
Strain Relaxation ◽  
Multiple Quantum Well ◽  
Light Output ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Growth Interruption ◽  
Aln Buffer

We demonstrate the highly efficient, GaN-based, multiple-quantum-well light-emitting diodes (LEDs) grown on Si (111) substrates embedded with the AlN buffer layer using NH3 growth interruption. Analysis of the materials by the X-ray diffraction omega scan and transmission electron microscopy revealed a remarkable improvement in the crystalline quality of the GaN layer with the AlN buffer layer using NH3 growth interruption. This improvement originated from the decreased dislocation densities and coalescence-related defects of the GaN layer that arose from the increased Al migration time. The photoluminescence peak positions and Raman spectra indicate that the internal tensile strain of the GaN layer is effectively relaxed without generating cracks. The LEDs embedded with an AlN buffer layer using NH3 growth interruption at 300 mA exhibited 40.9% higher light output power than that of the reference LED embedded with the AlN buffer layer without NH3 growth interruption. These high performances are attributed to an increased radiative recombination rate owing to the low defect density and strain relaxation in the GaN epilayer.

Effects of the Sputtering Time of AlN Buffer Layer on the Quality of ZnO Thin Films

2014 ◽  
Vol 881-883 ◽  
pp. 1117-1121 ◽  
Author(s):  
Xiang Min Zhao
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
Rf Magnetron Sputtering ◽  
Buffer Layers ◽  
Zno Thin Films ◽  
Zno Films ◽  
Si Substrates ◽  
Atomic Force ◽  
Structure Morphology ◽  
Aln Buffer

ZnO thin films with different thickness (the sputtering time of AlN buffer layers was 0 min, 30 min,60 min, and 90 min, respectively) were prepared on Si substrates using radio frequency (RF) magnetron sputtering system.X-ray diffraction (XRD), atomic force microscope (AFM), Hall measurements setup (Hall) were used to analyze the structure, morphology and electrical properties of ZnO films.The results show that growth are still preferred (002) orientation of ZnO thin films with different sputtering time of AlN buffer layer,and for the better growth of ZnO films, the optimal sputtering time is 60 min.

III-Nitride Growth on Lithium Niobate: A New Substrate Material for Polarity Engineering in III-Nitride Heteroepitaxy

2002 ◽  
Vol 743 ◽  
Author(s):  
W. Alan Doolittle ◽  
Gon Namkoong ◽  
Alexander Carver ◽  
Walter Henderson ◽  
Dieter Jundt ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Lattice Mismatch ◽  
Substrate Material ◽  
Buffer Layers ◽  
Initial Growth ◽  
Periodically Poled ◽  
Film Adhesion ◽  
Electro Optic ◽  
Bandgap Semiconductors ◽  
Aln Buffer

ABSTRACTHerein, we discuss the use of a novel new substrate for III-Nitride epitaxy, Lithium Niobate. It is shown that Lithium Niobate (LN) has a smaller lattice mismatch to III-Nitrides than sapphire and can be used to control the polarity of III-Nitride films grown by plasma assisted molecular beam epitaxy. Results from initial growth studies are reported including using various nitridation/buffer conditions along with structural and optical characterization. Comparisons of data obtained from GaN and AlN buffer layers are offered and details of the film adhesion dependence on buffer layer conditions is presented. Lateral polarization heterostructures grown on periodically poled LN are also demonstrated. While work is still required to establish the limits of the methods proposed herein, these initial studies offer the promise for mixing III-Nitride semiconductor materials with lithium niobate allowing wide bandgap semiconductors to utilize the acoustic, pyroelectric/ferroelectric, electro-optic, and nonlinear optical properties of this new substrate material as well as the ability to engineer various polarization structures for future devices.

Sn-based Group-IV Semiconductors on Si: New Infrared Materials and New Templates for Mismatched Epitaxy

2005 ◽  
Vol 891 ◽  
Author(s):  
John Tolle ◽  
Radek Roucka ◽  
Vijay D'Costa ◽  
Jose Menendez ◽  
Andrew Chizmeshya ◽  
...  
Keyword(s):  
Band Gap ◽  
Buffer Layer ◽  
Lattice Mismatch ◽  
Group Iv ◽  
Buffer Layers ◽  
Direct Band Gap ◽  
Group Iv Semiconductors ◽  
Direct Band ◽  
Infrared Materials ◽  
Edge Dislocations

ABSTRACTWe report growth and properties of GeSn and SiGeSn alloys on Si (100). These materials are prepared using a novel CVD approach based on reactions of Si-Ge hydrides and SnD4. High quality GeSn films with Sn contents up to 20%, and strain free microstructures have been obtained. The lattice mismatch between the films and Si is relieved by Lomer edge dislocations located at the interface. This material is of interest due to the predicted cross-over to a direct gap semiconductor for moderate Sn concentrations. We find that the direct band gap, and, consequently, the main absorption edge, shifts monotonically to lower energies as the Sn concentration is increased. The compositional dependence of the direct band gap shows a strong bowing, such that the direct band gap is reduced to 0.4 eV (from 0.8 eV for pure Ge) for a concentration of 14% Sn. The ternary SiGeSn alloy has been grown for the first time on GeSn buffer layers. This material opens up entirely new opportunities for strain and band gap engineering using group-IV materials via decoupling of strain and composition. Our SiGeSn layers have lattice constants above and below that of pure Ge, and depending on the thickness and composition of the underlying buffer layer they can be grown relaxed, with compressive, or with tensile strain. In addition to acting as a buffer layer for the growth of SiGeSn, we have found that GeSn can act as a template for the subsequent growth of a variety of materials, including III-V semiconductors.

GaN ON SILICON SUBSTRATE WITH AlN BUFFER LAYER FOR UV PHOTODIODE

2012 ◽  
Vol 21 (01) ◽  
pp. 1250014 ◽  
Author(s):  
L. S. CHUAH ◽  
S. M. THAHAB ◽  
Z. HASSAN
Keyword(s):  
Schottky Barrier ◽  
Buffer Layer ◽  
Barrier Height ◽  
Silicon Substrate ◽  
Dark Current ◽  
Schottky Barrier Height ◽  
Buffer Layers ◽  
Current Ratio ◽  
Principal Mechanism ◽  
Aln Buffer

Nitrogen plasma-assisted molecular beam epitaxy (PAMBE) deposited GaN thin films on (111) n-type silicon substrate with different thickness AlN buffer layers are investigated and distinguished by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman scattering. The thickness of AlN buffer layer ranged from 200 nm to 300 nm. Besides that, the electrical characteristics of the GaN thin film for ultraviolet detecting utilizations are studied by calculating the photo current/dark current ratio on a metal-semiconductor-metal (MSM) photodiode with and without the illumination of Hg-lamp source. The devices have been tested over room temperature (RT). The photocurrent analysis, together with the study of Schottky barrier height (SBH) development, ascertain that the principal mechanism of photo transport is thermionic emission. The photocurrent value is rigorously dependent on Schottky barrier height. The GaN/AlN(200 nm)/n-Si MSM photodiode produces the highest photo/dark current ratio for the lowest strain that consists of the GaN film grown on the AlN (200 nm) buffer layer.

scholarly journals Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

1999 ◽  
Vol 4 (S1) ◽  
pp. 417-422 ◽  
Author(s):  
E. C. Piquette ◽  
P. M. Bridger ◽  
R. A. Beach ◽  
T. C. McGill
Keyword(s):  
Surface Morphology ◽  
Buffer Layer ◽  
Flux Ratio ◽  
Plasma Source ◽  
Growth Conditions ◽  
Nitrogen Plasma ◽  
Layer Growth ◽  
Buffer Layers ◽  
Flat Surfaces ◽  
Aln Buffer

The surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than 1 nm RMS.

Microstructures of AlN Buffer Layers for the Growth of GaN on (0001) Al2O3

1996 ◽  
Vol 449 ◽  
Author(s):  
M. Yeadon ◽  
W. Kim ◽  
A. E. Botchkarev ◽  
S. N. Mohammad ◽  
H. Morkoc ◽  
...  
Keyword(s):  
Lattice Mismatch ◽  
Wide Band ◽  
Buffer Layers ◽  
Initial Growth ◽  
Nitridation Time ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Aln Buffer ◽  
Nitride Layers

ABSTRACTIll-nitride semiconductors are emerging as highly promising candidates for the fabrication of wide band-gap electronic and opto-electronic devices. Sapphire ((α-A12O3) is currently one of the primary substrates of choice for the growth of GaN despite a large lattice mismatch. Significant improvements in the quality of III-nitride layers have been demonstrated by exposure of the substrate to reactive nitrogen species followed by deposition of a low temperature AIN or GaN buffer layer. In this paper we present a study of the evolution of the surface topography and defect microstructure of nitrided α-A12O3 substrates and AIN buffer layers deposited by reactive molecular beam epitaxy (RMBE). Their influence on the morphology and properties of GaN layers is also discussed. Both nitridation time and AIN deposit thickness were varied systematically, at different temperatures and buffer growth rates. The microstructures were characterized using the atomic force microscope (AFM) and transmission electron microscope (TEM). Initial growth studies are ideally suited to in-situ experiments, and further investigations are also in progress using a unique UHV TEM with the facility for in-situ RMBE.

Defects and Interfaces in GaN Epitaxy

MRS Bulletin ◽  
1997 ◽  
Vol 22 (2) ◽  
pp. 51-57 ◽  
Author(s):  
F.A. Ponce
Keyword(s):  
Thermal Expansion ◽  
High Performance ◽  
Lattice Mismatch ◽  
Thermal Strain ◽  
Chemical Vapor ◽  
Visible Spectrum ◽  
Lattice Parameter ◽  
Buffer Layers ◽  
Semiconductor Films ◽  
Recent Developments

The recent developments in III-V-nitride thin-film technology has produced significant advances in high-performance devices operating in the blue and green range of the visible spectrum. These materials are grown by metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Highly specular surfaces are possible by use of low-temperature buffer layers following the method developed by Akasaki et al. The thin films thus grown have an interesting microstructure, quite different from other known semiconductors. In particular, epilayers with high optoelectronic performance are characterized by high dislocation densities, several orders of magnitude above those found in other optoelectronic semiconductor films. The lattice mismatch between sapphire and GaN is ∼14%, and the thermal-expansion difference is close to 80%. In spite of these large differences, little thermal strain is measurable at room temperature in epilayers grown at temperatures above 1000°C. Epitaxy on other systems, like SiC, with much better similarity in lattice parameter and thermal-expansion characteristics, has failed to produce better performance than films grown on sapphire. The origin of these puzzling properties of nitrides on sapphire rests in its microstructure. This article presents a survey of the microstructure associated with epitaxy of nitrides by MOCVD.

Epitaxial tilt of partially relaxed InGaAs layers grown on (100) GaAs substrates

1992 ◽  
Vol 70 (10-11) ◽  
pp. 838-842
Author(s):  
P. Maigné ◽  
A. P. Roth ◽  
C. Desruisseaux ◽  
D. Coulas
Keyword(s):  
Residual Strain ◽  
Gaas Substrate ◽  
Strain Relaxation ◽  
Azimuthal Angle ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Mismatch Strain ◽  
Gaas Substrates

The structural properties of partially relaxed InxGa1−xAs layers grown on (100) GaAs substrates have been investigated, using high-resolution X-ray diffraction, in order to better understand the mechanisms responsible for the relaxation of the mismatch strain. From symmetric [400] reflections recorded as functions of the azimuthal angle [Formula: see text], the (100) InGaAs planes are found to be tilted with respect to the (100) GaAs substrate planes. The tilt magnitude is first seen to decrease then to increase with layer thickness. The direction of the tilt changes from [01-1] to [00-1] in the range of thickness investigated. From [422] asymmetric reflections, the average in-plane lattice parameter, the indium composition as well as the percentage of relaxation can be measured. Our values for relaxation are in qualitative agreement with the Dodson and Tsao model of strain relaxation (Appl. Phys. Lett. 51, 1710 (1987)). In addition, our data show an anisotropy in residual strain along <011> directions. This anisotropy increases with the amount of strain relieved and changes the crystal symmetry of the cell from tetragonal to monoclinic. This monoclinic symmetry can be characterized by an angle β that measures the angle between 90° and the inner angles of the new crystallographic cell. As for the anisotropy in residual strain, |3 increases with the amount of strain relieved. Correlations between tilt magnitude and tilt direction with the formation of 60° type dislocations are discussed.

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