scholarly journals Microstructures of GaN and InxGa1-xN Films Grown by MOCVD on freestanding GaN Templates

2002 ◽  
Vol 722 ◽  
Author(s):  
J. Jasinski ◽  
Z. Liliental-Weber ◽  
D. Huang ◽  
M. A. Reshchikov ◽  
F. Yun ◽  
...  
Keyword(s):  
Lattice Parameter ◽  
Point Of View ◽  
Structural Quality ◽  
Threading Dislocations ◽  
Structural Studies ◽  
Transmission Electron ◽  
Nitride Layers ◽  
Convergent Beam ◽  
Gan Film

AbstractWe summarize structural properties of thick HVPE GaN templates from the point of view of their application as substrates for growth of nitride layers. This is followed by the results of optical and structural studies, mostly transmission electron microscopy, of nitride layers grown by MOCVD on top of the HVPE substrates. The results indicate high structural quality of these layers with a low density of threading dislocations (in the range of 106 cm-2). Convergent beam electron diffraction studies showed that the MOCVD GaN films have Ga-polarity, the same polarity as the HVPE GaN substrates. Structural studies of an InGaN layer grown on top of the MOCVD GaN film showed the presence of two layers, which differed in lattice parameter and composition. The upper layer, on the top of the structure had a clattice parameter about 2 % larger than that of GaN and contained 10.3 ± 0.8 % of In. Values measured for the thinner, intermediate layer adjacent to the GaN layer were about 2.5 times lower.

scholarly journals Влияние морфологии буферного слоя AlN на структурное качество полуполярного слоя GaN, выращенного на подложке Si(001), по данным просвечивающей электронной микроскопии

2022 ◽  
Vol 48 (5) ◽  
pp. 51
Author(s):  
Д.А. Кириленко ◽  
А.В. Мясоедов ◽  
А.Е. Калмыков ◽  
Л.М. Сорокин
Keyword(s):  
Gallium Nitride ◽  
Buffer Layer ◽  
Structural Features ◽  
Nitride Layer ◽  
Structural Quality ◽  
Threading Dislocations ◽  
Interface Morphology ◽  
Transmission Electron ◽  
Dislocations Density

Structural features of the interface between semipolar gallium nitride layer and buffer layer of aluminum nitride grown on a SiC/Si(001) template misoriented by an angle of 7° were studied by high-resolution transmission electron microscopy. The effect of interface morphology on the structural quality of the gallium nitride layer is revealed: faceted structure the surface of the buffer layer reduces the threading dislocations density.

Measurement of lattice parameter at the nanometer scale using convergent-beam microdiffraction from a thermal emission source

1993 ◽  
Vol 51 ◽  
pp. 690-691
Author(s):  
W. T. Pike
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Thermal Emission ◽  
Lattice Parameter ◽  
Scanning Transmission Electron Microscope ◽  
Emission Source ◽  
Device Structure ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Convergent Beam

With the advent of crystal growth techniques which enable device structure control at the atomic level has arrived a need to determine the crystal structure at a commensurate scale. In particular, in epitaxial lattice mismatched multilayers, it is of prime importance to know the lattice parameter, and hence strain, in individual layers in order to explain the novel electronic behavior of such structures. In this work higher order Laue zone (holz) lines in the convergent beam microdiffraction patterns from a thermal emission transmission electron microscope (TEM) have been used to measure lattice parameters to an accuracy of a few parts in a thousand from nanometer areas of material.Although the use of CBM to measure strain using a dedicated field emission scanning transmission electron microscope has already been demonstrated, the recording of the diffraction pattern at the required resolution involves specialized instrumentation. In this work, a Topcon 002B TEM with a thermal emission source with condenser-objective (CO) electron optics is used.

The Influence of the Temperature Gradient on the Defect Structure of 3C-SiC Grown Heteroepitaxially on 6H-SiC by Sublimation Epitaxy

2010 ◽  
Vol 645-648 ◽  
pp. 367-370 ◽  
Author(s):  
Maya Marinova ◽  
Alkyoni Mantzari ◽  
Milena Beshkova ◽  
Mikael Syväjärvi ◽  
Rositza Yakimova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Temperature Gradient ◽  
Defect Structure ◽  
Temperature Gradients ◽  
Structural Quality ◽  
Fault Density ◽  
Transmission Electron

In the present work the structural quality of 3C-SiC layers grown by sublimation epitaxy is studied by means of conventional and high resolution transmission electron microscopy. The layers were grown on Si-face 6H-SiC nominally on-axis substrates at a temperature of 2000°C and different temperature gradients, ranging from 5 to 8 °C /mm. The influence of the temperature gradient on the structural quality of the layers is discussed. The formation of specific twin complexes and conditions for lower stacking fault density are investigated.

scholarly journals Structural Defects in Laterally Overgrown GaN Layers Grown on Non-polar Substrates

2006 ◽  
Vol 955 ◽  
Author(s):  
Zuzanna Liliental-Weber ◽  
X. Ni ◽  
H. Morkoc
Keyword(s):  
Large Angle ◽  
Stacking Faults ◽  
Growth Direction ◽  
Convergent Beam Electron Diffraction ◽  
Structural Defects ◽  
Threading Dislocations ◽  
Beam Electron ◽  
Transmission Electron ◽  
Wing Width ◽  
Convergent Beam

ABSTRACTTransmission electron microscopy was used to study defects in lateral epitaxial layers of GaN which were overgrown on a template of a-plane (1120) GaN grown on (1102) r-plane Al2O3. A high density of basal stacking faults is formed in these layers because the c-planes of wurtzite structure are arranged along the growth direction. Density of these faults is decreasing at least by two orders of magnitude lower in the wings compared to the seed areas. Prismatic stacking faults and threading dislocations are also observed, but their densities drastically decrease in the wings. The wings grow with opposite polarities and the Ga-wing width is at least 6 times larger than N-wing and coalescence is rather difficult. Some tilt and twist was detected using Large Angle Convergent Beam Electron Diffraction.

Tem Study of the Structure of Mbe GaAs Layers Grown at Low Temperature

1990 ◽  
Vol 198 ◽  
Author(s):  
Zuzanna Liliental-Weber
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Molecular Beam ◽  
Critical Thickness ◽  
Stacking Faults ◽  
Structural Quality ◽  
Crystalline Perfection ◽  
Transmission Electron ◽  
Low Temperature Gaas

ABSTRACTThe structural quality of GaAs layers grown at 200°C by molecular beam epitaxy (MBE) was investigated by transmission electron microscopy (TEM). We found that a high crystalline perfection can be achieved in the layers grown at this low temperature for thickness up to 3 μm. In some samples we observed pyramid-shaped defects with polycrystalline cores surrounded by microtwins, stacking faults and dislocations. The size of these cores increased as the growth temperature was decreased and as the layer thickness was increased. The upper surface of layers with pyramidal defects became polycrystalline at a critical thickness of the order of 3μm. We suggested that the low-temperature GaAs becomes polycrystalline at a critical thickness either because of a decrease in substrate temperature during growth or because strain induced by excess As incorporated in these layers leads to the formation of misoriented GaAs nuclei, thereby initiating polycrystalline growth. The pyramidal shape of the defects results from a growth-rate hierarchy of the low index planes in GaAs.

MOCVD Growth of GaN Films on Lattice-Matched Oxide Substrates

1996 ◽  
Vol 449 ◽  
Author(s):  
O. M. Kryliouk ◽  
T. W. Dann ◽  
T. J. Anderson ◽  
H. P. Maruska ◽  
L. D. Zhu ◽  
...  
Keyword(s):  
Structural Quality ◽  
Film Properties ◽  
Cross Sectional ◽  
Substrate Orientation ◽  
Mocvd Growth ◽  
Dislocation Densities ◽  
Oxide Substrates ◽  
Lattice Matched ◽  
Gan Film

ABSTRACTThe use of the nearly lattice-matched oxide substrates LiGaO2 and LiAlO2 has been explored for growth of GaN by MOCVD. As compared to the quality of films grown on sapphire, only growth on LiGaO2 yielded good quality films, and required use of nitrogen as the carrier gas. Furthermore, high structural quality films were grown on LiGaO2 at temperatures as low as 850°C. Dislocation densities estimated from cross-sectional TEM micrographs were found to be as low as 107 cm-2 . HRTEM studies revealed deformations at the surface of the LiGaO2 adjacent to deposited GaN films, indicating possible interracial reactions which may affect the film properties. The GaN film orientations corresponded directly to the substrate orientation, viz., ({0001}/{001} and {1102}/{101}).

A Comparison of the Structural Quality of High-In Content InGaAsN Films Grown on InGaAs Pseudosubstrate and on GaAs Substrate

2007 ◽  
Vol 31 ◽  
pp. 221-223
Author(s):  
S. Sanorpim ◽  
P. Kongjaeng ◽  
R. Katayama ◽  
Kentaro Onabe
Keyword(s):  
Electron Microscopy ◽  
Gaas Substrate ◽  
Misfit Strain ◽  
The Other ◽  
Buffer Layers ◽  
Structural Quality ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
Lattice Matched

The use of an InGaAs buffer layer was applied to the growth of thick InxGa1-xAs1-yNy layers with higher In contents (x > 30%). In order to obtain the lattice-matched InGaAsN layer having the bandgap of 1.0 eV, the In0.2Ga0.8As was chosen. In this work, the In0.3Ga0.7As0.98N0.02 layers were successfully grown on closely lattice-matched In0.2Ga0.8As buffer layers (InGaAsN/InGaAs). Structural quality of such layers is discussed in comparison with those of the In0.3Ga0.7As0.98N0.02 layers grown directly on the GaAs substrate (InGaAsN/GaAs). Based on the results of transmission electron microscopy, the misfit dislocations (MDs), which are located near the InGaAsN/GaAs heteroepitaxial interface, are visible by their strain contrast. On the other hand, no generation of the MDs is evidenced in the InGaAsN layer grown on the In0.2Ga0.8As pseudosubstrate. Our results demonstrate that a reduction of misfit strain though the use of the pseudosubstrate made possible the growth of high In-content InGaAsN layers with higher crystal quality to extend the wavelength of InGaAsN material.

Optical properties of GaN with Ga and N polarity

2001 ◽  
Vol 693 ◽  
Author(s):  
M. A. Reshchikov ◽  
D. Huang ◽  
F. Yun ◽  
P. Visconti ◽  
T. King ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Radiative Efficiency ◽  
Sapphire Substrates ◽  
Transmission Electron ◽  
And Inversion

AbstractWe compared photoluminescence (PL) and cross-sectional transmission electron microscopy (TEM) characteristics of GaN samples with Ga and N polarities grown by molecular beam epitaxy (MBE) on sapphire substrates. Ga-polar films grown at low temperature typically have very smooth surfaces, which are extremely difficult to etch with acids or bases. In contrast, the N-polar films have rougher surfaces and can be easily etched in hot H3PO4 or KOH. The quality of the X-ray diffraction spectra is also much better in case of Ga-polar films. Surprisingly, PL efficiency is always much higher in the N-polar GaN, yet the features and shape of the PL spectra are comparable for both polarities. We concluded that, despite the excellent quality of the surface, MBE-grown Ga-polar GaN layers contain higher concentration of nonradiative defects. From the analyses of cross-sectional TEM investigations, we have found that Ga-polar films have high density of threading dislocations (5x109 cm-2) and low density of inversion domains (1x107 cm-2). For N-polar GaN the situation is the reverse: the density of dislocations and inversion domains are 5x108 and ~1x1011 cm-2, respectively. One of the important conclusions derived from the combined PL and TEM study is that inversion domains do not seem to affect the radiative efficiency very adversly, whereas dislocations reduce it significantly.

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