scholarly journals Can Laterally Overgrown GaN Layers be free of Structural Defects?

2000 ◽  
Vol 639 ◽  
Author(s):  
D. Cherns ◽  
Z. Liliental-Weber
Keyword(s):  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Structural Defects ◽  
Shear Stresses ◽  
Threading Dislocations ◽  
Cross Sectional ◽  
Plan View ◽  
Transmission Electron ◽  
Half Loop ◽  
Convergent Beam

ABSTRACTTransmission electron microscopy has been used to examine dislocations present in an epitaxial laterally overgrown (ELOG) sample of GaN grown on (0001)sapphire. Studies of both plan-view and cross-sectional samples revealed arrays of dislocations present in the (11-20) boundary between the seed and the wing (overgrown) material and at the meeting front between adjacent wings, as well as dislocations in the form of half-loops extending into the wing regions. Both the boundary and half-loop dislocations had 1/3<11-20> Burgers vectors which were either perpendicular (boundary dislocations) or at 30°s (half-loops) to the boundary plane. Large angle convergent beam electron diffraction was used to show that the boundary dislocations and halfloops correlated respectively with tilts and twists of the wing material about (11-20). A model is proposed whereby the half-loops are generated from threading dislocations by shear stresses acting along the stripe direction. The origin, and elimination, of these stresses is discussed.

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.

Coherent of PbTe/MgO Bi-Crystals and its Multislice Simulation

1997 ◽  
Vol 3 (S2) ◽  
pp. 1063-1064
Author(s):  
N. Tanaka ◽  
M. Egi ◽  
K. Kimoto
Keyword(s):  
Electron Diffraction ◽  
Science Studies ◽  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Cross Sectional ◽  
Plan View ◽  
Beam Electron ◽  
Interference Fringes ◽  
Convergent Beam ◽  
Interface Structures

Atomic structure of hetero-interfaces such as semiconductor/oxide is recently much interested from the viewpoints of the device engineering as well as the interface science. Studies of the interface structures have been performed by transmission electron microscopy (TEM)[1], large-angle convergent beam electron diffraction[2] in the cross-sectional observation mode, and by X-ray diffraction[3], TEM[4] and CBED[5] in the plan-view mode. In the present study we applied a coherent convergent beam electron diffraction (c-CBED) technique to the analysis of the rigid-body shift between vacuum-deposited PbTe and MgO (001) thin crystals in the plan-view mode. The c-CBED technique was originated in nano-diffraction experiments by Cowley[6] and the theoretical analysis by Spence[7]. These results suggested a possibility of direct structure-phase determination from the interference fringes formed at coherent overlaps between the diffraction disks. This technique has been recently revived using TEM on SiC by Vine et al.[8] The present study is the first to be concerned with the analysis of interference fringes in c-CBED patterns from epitaxially grown bi-crystals[9].

Chemical sensitivity of convergent beam electron diffraction on the stoichiometry of GaN

1995 ◽  
Vol 53 ◽  
pp. 148-149
Author(s):  
Zuzanna Liliental-Weber ◽  
Christian Kisielowski ◽  
Jack Washburn
Keyword(s):  
Electron Diffraction ◽  
Film Growth ◽  
Lattice Mismatch ◽  
Uv Light ◽  
Convergent Beam Electron Diffraction ◽  
Structural Defects ◽  
Plan View ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam

III-V nitride thin film growth has attracted considerable attention because it now seems feasible to engineer semiconductor band gaps between 2.1 and 6.2 eV. One of the challenges coming with this development is related to the fact that structural perfection seems not to correlate directly with optical properties such as the emission of blue-green or UV light in GaN. In order to better understand this material High Resolution Transmission Electron Microscopy (HREM) and Convergent Beam Electron Diffraction (CBED) experiments were used to study structural defects in GaN thin films. Experiments were performed with a Topcon 002B and ARM operating at 200 and 800 KeV, respectively, and were guided by image simulations. Results of parallel luminescence studies will be published elsewhere.Plan-view micrographs of GaN grown on the (0001) basal plane of A12O3 with a lattice mismatch of 14% show small angle grain boundaries which divide the layer into large subgrains of about 800 nm diameter. Other defects visible in the plan-view micrographs are threading dislocations and planar defects lying parallel to the {1010} planes of the GaN.

Plan-View CBED Studies of Nio-Zro2(CaO) Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
V.P. Dravid ◽  
M.R. Notis ◽  
C.E. Lyman ◽  
A. Revcolevschi
Keyword(s):  
Electron Diffraction ◽  
Convergent Beam Electron Diffraction ◽  
Low Energy ◽  
Directionally Solidified ◽  
Plan View ◽  
Beam Electron ◽  
Transmission Electron ◽  
Interfacial Defects ◽  
Convergent Beam ◽  
Lamellar Interfaces

ABSTRACTLow energy lamellar interfaces in the directionally solidified eutectic (DSE) NiO-ZrO2(CaO) have been investigated using transmission electron diffraction and imaging. The symmetry of this bicrystal and an aspect of interfacial relaxations in the form of symmetry lowering in-plane rigid body translation (RBT) have been explored by performing convergent beam electron diffraction (CBED) experiments of plan-view bicrystals. Edge-on interfaces have also been studied by conventional and high resolution transmission electron microscopy (CTEM and HRTEM respectively), and electron diffraction fine structure analysis. Despite certain experimental difficulties due to interfacial defects and strain, plan-view CBED patterns offered valuable information concerning bicrystal symmetry and indicated no symmetry lowering RBT in this bicrystal. The suitability of plan-view CBED is briefly discussed in view of its potential as a technique to determine bicrystal symmetry and RBT.

Microstructural And Microchemical Analysis of Chalcopyrite Cu(In,Ga)Se2 Films

2003 ◽  
Vol 763 ◽  
Author(s):  
Chun-Ming Li ◽  
Chang-Hui Lei ◽  
Ian M. Robertson ◽  
Angus Rockett
Keyword(s):  
Grain Boundaries ◽  
High Performance ◽  
Structural Defects ◽  
Ion Milling ◽  
Mechanical Grinding ◽  
Cross Sectional ◽  
Plan View ◽  
Microchemical Analysis ◽  
Transmission Electron ◽  
Means Of Transmission

AbstractThe microstructure and microchemistry of Cu(In, Ga)Se2 (CIGS) films have been analyzed by means of transmission electron microscopy (TEM). Specimens were obtained from a number of groups producing high-performance solar cells from these materials. Both plan-view and cross-sectional TEM samples were prepared by mechanical grinding and ion milling. Twins can be found easily within the films while dislocations are present only in a few grains and with low density. No extended structural defects such as stacking faults were discovered. X-ray energy dispersive spectroscopy was used to study the chemical composition of grains and grain boundaries. Experimental results showed no difference between the composition in the grain interiors and the grain boundary. In addition, there is no obvious enhancement of oxygen and sodium at grain boundaries. Structural depth dependences were also not found.

scholarly journals Dislocation Analysis in SiGe Heterostructures by Large-Angle Convergent Beam Electron Diffraction

Crystals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 5
Author(s):  
Heiko Groiss
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Strain Relaxation ◽  
Large Angle ◽  
Convergent Beam Electron Diffraction ◽  
Self Organization ◽  
Detailed Knowledge ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam

Dislocations play a crucial role in self-organization and strain relaxation mechanisms in SiGe heterostructures. In most cases, they should be avoided, and different strategies exist to exploit their nucleation properties in order to manipulate their position. In either case, detailed knowledge about their exact Burgers vectors and possible dislocation reactions are necessary to optimize the fabrication processes and the properties of SiGe materials. In this review a brief overview of the dislocation mechanisms in the SiGe system is given. The method of choice for dislocation characterization is transmission electron microscopy. In particular, the article provides a detailed introduction into large-angle convergent-beam electron diffraction, and gives an overview of different application examples of this method on SiGe structures and related systems.

The Art and Application of Large Angle Convergent Beam Electron Diffraction

2012 ◽  
Vol 186 ◽  
pp. 16-19 ◽  
Author(s):  
Elżbieta Jezierska
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Antiphase Boundary ◽  
Antiphase Domain ◽  
Dark Field ◽  
Convergent Beam Electron Diffraction ◽  
Intermetallic Alloys ◽  
Beam Electron ◽  
Transmission Electron ◽  
Convergent Beam

The antiphase domain structure in Ni3Al and Al3Ti+Cu intermetallic alloys was recognized by conventional transmission electron microscopy and large angle convergent beam electron diffraction methods. In the case of antiphase boundary the superlattice excess line is split into two lines with equal intensity on bright and dark field LACBED pattern. This splitting can be considered as typical and used to identify APBs. The recognition between perfect structure of the defect-free matrix and the screw deviation around the nanopipes in GaN epilayers was performed with high accuracy using Zone Axis LACBED images.

Influence of Rapid Thermal Annealing on Shallow BF2 Implantation into Pre-Amorphized Silicon

1983 ◽  
Vol 23 ◽  
Author(s):  
W. Maszara ◽  
C. Carter ◽  
D. K. Sadana ◽  
J. Liu ◽  
V. Ozguz ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Ion Beam ◽  
Liquid Nitrogen Temperature ◽  
Structural Defects ◽  
Structural Quality ◽  
Halogen Lamp ◽  
Cross Sectional ◽  
Plan View ◽  
Transmission Electron

ABSTRACTLow energy, shallow BF2+ implants were carried out at room or liquid nitrogen temperature into deep pre-amorphized (100) Si for better control of the dopant profile and post-annealing structural defects. Cross sectional and angle polished plan view transmission electron microscopy were used to study the structural quality of the implanted layer, while SIMS provided a chemical profile. Four types of structural defects were observed in BF2+ implanted, pre-amorphized samples following rapid thermal annealing with a halogen lamp. An in-situ ion beam annealing and the presence of F in the Si lattice were related to the creation of the defects. Good correlations between F gettering and TEM observed defects were found to exist. Implantation of B+ into a pre-amorphized Si surface and subsequent rapid thermal annealing was found to produce a wide defect-free surface layer.

Formation of Subthreshold Defects in Erbium Implanted Silicon

1998 ◽  
Vol 532 ◽  
Author(s):  
C. Flink ◽  
S. Mui ◽  
H. Gottschalk ◽  
J. Palm ◽  
E. R. Weber
Keyword(s):  
Electron Microscopy ◽  
Convergent Beam Electron Diffraction ◽  
Concentration Profiles ◽  
Primary Defect ◽  
Cross Sectional ◽  
Beam Electron ◽  
Defect Clusters ◽  
Excess Silicon ◽  
Transmission Electron ◽  
Convergent Beam

ABSTRACTIn this work we present the first quantitative approach to model subthreshold defects. Using cross-sectional Transmission Electron Microscopy (XTEM) and Convergent Beam Electron Diffraction (CBED), we studied subthreshold defects in Cz-silicon that followed a deep implantation of erbium, and their interaction with co-implantations. The analyzed Frank loops show an increasing size by a factor of five with increasing depth in the wafer. The ratios of the number of condensed silicon atoms to the implant doses support a “+0.4 model” for the erbium and a “+0.07 model” for the oxygen as a co-implant. Our results indicate that a “push away” mechanism produces the excess silicon atoms in the case of interstitial implant atoms. The observed loop size depth distributions helped to reveal the condensation mechanism of subthreshold defects. This mechanism is described by the relaxation of excess silicon atoms on primary defect clusters. The decreasing concentration profiles of the primary defect clusters together with the high diffusivity of silicon interstitials results in a number of condensed silicon atoms per loop that increases with the depth in the wafer.

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