Residual Strain and Defect Analysis in as Grown and Annealed SiGe Layers

1991 ◽  
Vol 220 ◽  
Author(s):  
A. R. Powell ◽  
R. A. Kubiak ◽  
T. E. Whall ◽  
E. H. C. Parker ◽  
D. K. Bowen
Keyword(s):  
Residual Strain ◽  
Buffer Layers ◽  
Limited Area ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
High Temperature Anneal ◽  
Dislocation Densities ◽  
Acceptable Quality ◽  
Strained Sige

ABSTRACTIn this paper we address the problem of producing SiGe buffer layers of acceptable quality for the growth of symmetrically strained SiGe structures. Initially we consider SiGe layers grown to well beyond the metastable critical thickness and examine the degree of residual strain both as - grown and post anneal. The defect levels in metastable SiGe layers following high temperature anneal were also studied. A buffer layer was grown consisting of stacked metastable SiGe layers each of which is annealed in situ prior to the growth of the next layer and terminating with a 0.45 SiGe alloy. This produces nearly fully relaxed 1.15pim thick structures with threading dislocation densities of 4 × 106cm−2. Limited area growth on Si suggests that elastically relaxed material free of both threading and misfit dislocations can be produced.

Equilibrium Lattice Relaxation and Misfit Dislocations in Continuously- and Step-Graded InxGa1-xAs/GaAs (001) and GaAs1-yPy/GaAs (001) Metamorphic Buffer Layers

2015 ◽  
Vol 24 (03n04) ◽  
pp. 1520009 ◽  
Author(s):  
Tedi Kujofsa ◽  
John E. Ayers
Keyword(s):  
Dislocation Density ◽  
Buffer Layer ◽  
Minimum Energy ◽  
Lattice Relaxation ◽  
Structure Type ◽  
Elastic Stiffness ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Metamorphic Buffer

The inclusion of metamorphic buffer layers (MBL) in the design of lattice-mismatched semiconductor heterostructures is important in enhancing reliability and performance of optical and electronic devices. These metamorphic buffer layers usually employ linear grading of composition, and materials including InxGa1-xAs and GaAs1-yPy have been used. Non-uniform and continuously graded profiles are beneficial for the design of partially-relaxed buffer layers because they reduce the threading dislocation density by allowing the distribution of the misfit dislocations throughout the metamorphic buffer layer, rather than concentrating them at the interface where substrate defects and tangling can pin dislocations or otherwise reduce their mobility as in the case of uniform compositional growth. In this work we considered heterostructures involving a linearly-graded (type A) or step-graded (type B) buffer layer grown on a GaAs (001) substrate. For each structure type we present minimum energy calculations and compare the cases of cation (Group III) and anion (Group V) grading. In addition, we studied the (i) average and surface in-plane strain and (ii) average misfit dislocation density for heterostructures with various thickness and compositional profile. Moreover, we show that differences in the elastic stiffness constants give rise to significantly different behavior in these two commonly-used buffer layer systems.

Strategies For Direct Monolithic Integration of AlxGa(1−x)As/InxGa(1−x)As LEDS and Lasers On Ge/GeSi/Si Substrates Via Relaxed Graded GexSi(1−x) Buffer Layers

2001 ◽  
Vol 692 ◽  
Author(s):  
Michael E. Groenert ◽  
Christopher W. Leitz ◽  
Arthur J. Pitera ◽  
Vicky K. Yang ◽  
Harry Lee ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Threshold Current ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Carrier Lifetimes ◽  
Si Substrates ◽  
Dislocation Densities ◽  
Minority Carrier Lifetimes ◽  
Current Densities ◽  
High Series

AbstractAlxGa(1−x)As/GaAs quantum well lasers have been demonstrated via organometallic chemical vapor deposition (OMCVD) on relaxed graded GexSi(1−x) virtual substrates on Si. Despite unoptimized laser structures with high series resistance and large threshold current densities, surface threading dislocation densities as low as 2×106 cm−2 enabled cw room-temperature lasing at a wavelength of 858nm. The laser structures are oxide-stripe gain-guided devices with differential quantum efficiencies of 0.16 and threshold current densities of 1550A/cm2. Identical devices grown on commercial GaAs substrates showed differential quantum efficiencies of 0.14 and threshold current densities of 1700A/cm2. This comparative data agrees with our previous measurements of near-bulk minority carrier lifetimes in GaAs grown on Ge/GeSi/Si substrates. A number of GaAs/Ge/Si integration issues including thermal expansion mismatch and Ge autodoping behavior in GaAs were overcome.

SiH4 exposure of GaN surfaces: A useful tool for highlighting dislocations

2005 ◽  
Vol 892 ◽  
Author(s):  
Rachel Oliver ◽  
Menno J. Kappers ◽  
Joy Sumner ◽  
Ranjan Datta ◽  
Colin J. Humphreys
Keyword(s):  
Atomic Force Microscopy ◽  
Vapour Phase ◽  
Threading Dislocation ◽  
Vapour Phase Epitaxy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dislocation Densities ◽  
Metal Organic ◽  
Organic Vapour

AbstractFast-turnaround, accurate methods for the assessment of threading dislocation densities in GaN are an essential research tool. Here, we present an in-situ surface treatment for use in MOVPE (metal-organic vapour phase epitaxy) growth, in which GaN is exposed to a SiH4 flux at 860 °C in the presence of NH3. Subsequent characterisation by atomic force microscopy shows that the treatment is effective in increasing edge and mixed/screw dislocation pit sizes on both n- and p-type material, and on partially coalesced GaN layers.

scholarly journals Снижение плотности прорастающих дислокаций в темплейтах AlN/c-сапфир, выращенных методом плазменно-активированной молекулярно-пучковой эпитаксии

2020 ◽  
Vol 46 (8) ◽  
pp. 36
Author(s):  
В.В. Ратников ◽  
Д.В. Нечаев ◽  
А.В. Мясоедов ◽  
О.А. Кошелев ◽  
В.Н. Жмерик
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Flux Ratio ◽  
Buffer Layers ◽  
Stress Generation ◽  
Threading Dislocation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Regimes ◽  
Dislocation Densities

Multiple-crystal X-ray diffraction and a multi-beam optical stress sensor were used to study AlN/c-sapphire templates grown by plasma-assisted molecular beam epitaxy. The influence of the nucleation and buffer layers growth regimes, temperature, the ratio between Al and N* growth fluxes on the stress generation and the character of the dislocation structure were analyzed. Templates with the best crystal quality with screw and edge threading dislocation densities in a range of 4∙10^8 and 8∙10^9 cm-2, respectively, were obtained at the flux ratio of Al to N* close to 1 by using two-stage temperature regimes.

Scaling laws for the reduction of threading dislocation densities in homogeneous buffer layers

1996 ◽  
Vol 80 (7) ◽  
pp. 3808-3816 ◽  
Author(s):  
J. S. Speck ◽  
M. A. Brewer ◽  
G. Beltz ◽  
A. E. Romanov ◽  
W. Pompe
Keyword(s):  
Scaling Laws ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Dislocation Densities

Tem Investigation of Al0.5Ga0.5As1-y Sby Buffer Layer Systems

1997 ◽  
Vol 484 ◽  
Author(s):  
E. Chen ◽  
J. S. Ahearn ◽  
K. Nichols ◽  
P. Uppal ◽  
D. C. Paine
Keyword(s):  
Buffer Layer ◽  
Active Regions ◽  
Dark Field ◽  
Layer Growth ◽  
Buffer Layers ◽  
Growth Surface ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Plan View ◽  
Dark Field Imaging

AbstractWe report on a TEM study of Sb-adjusted quaternary Al0.5Ga0.5As1-y Sby buffer-layers grown on <001> GaAs substrates. A series of structures were grown by MBE at 470°C that utilize a multilayer grading scheme in which the Sb content of Al0.5Ga0.5As1-ySby is successively increased in a series of eight 125 nm thick layers. Post growth analysis using conventional bright field and weak beam dark field imaging of these buffer layers in cross-section reveals that the interface misfit dislocations are primarily of the 60° type and are distributed through out the interfaces of the buffer layer. Plan view studies show that the threading dislocation density in the active regions of the structure (approximately 2 μm from the GaAs substrate) is 105–6/cm2 which is comparable to equivalent InxGa1−x As buffers. Weak Sb-As compositional modulations with a period of 1.8 nm were observed that provide a marker for establishing the planarity of the growth process. These features reveal that the growth surface remains planar through out the buffer layer growth sequence.

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.

TEM characterization of dislocation reduction processes in GaAs/Si

1989 ◽  
Vol 47 ◽  
pp. 590-591
Author(s):  
R.A. Herring ◽  
P.N. Uppal ◽  
S.P. Svensson ◽  
J.S. Ahearn
Keyword(s):  
Lattice Mismatch ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Growth Interface ◽  
Dislocation Reduction ◽  
Dislocation Densities ◽  
Threading Dislocation Density ◽  
Interfacial Dislocations ◽  
Strained Layer Superlattices

A high density of interfacial dislocations are needed at the GaAs/Si interface to alleviate the 4% lattice mismatch between GaAs and Si. Some remnant dislocations thread through the epilayer and follow the growth interface. Current growth methods are not able to obtain acceptable threading dislocation densities (104 – 105) for devices. Many methods can be used to reduce the number of threading dislocations which include misorienting the substrate to enhance the slip of dislocations on specific [110]{111} planes, annealing during and after growth, and adding strained layer superlattices (SLS's) to block dislocations. Conventional TEM (CTEM), performed using a JEM 100c, has been used to characterize threading dislocations in the epilayer of a GaAs/Si material where in situ thermal annealing and SLS's force dislocation reactions and thereby reduce the threading dislocation density. Using TEM we have viewed dislocations under many two-beam diffraction conditions and with the help of a stereogram have determined their Burgers vectors (b), line directions (u) and habit planes (R).

Comparison of Buffer Layer Grading Approaches in InGaAs/GaAs (001)

2020 ◽  
Vol 29 (01n04) ◽  
pp. 2040002
Author(s):  
Johanna Raphael ◽  
Tedi Kujofsa ◽  
J. E. Ayers
Keyword(s):  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Lower Surface ◽  
Dislocation Dynamics ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Dislocation Densities ◽  
Threading Dislocation Density ◽  
Dislocations Density ◽  
Graded Structures

Metamorphic semiconductor devices often utilize compositionally-graded buffer layers for the accommodation of the lattice mismatch with controlled threading dislocation density and residual strain. Linear or step-graded buffers have been used extensively in these applications, but there are indications that sublinear, superlinear, S-graded, or overshoot graded structures could offer advantages in the control of defect densities. In this work we compare linear, step-graded, and nonlinear grading approaches in terms of the resulting strain and dislocations density profiles using a state-of-the-art model for strain relaxation and dislocation dynamics. We find that sublinear grading results in lower surface dislocation densities than either linear or superlinear grading approaches.

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