Impact of interfacial misfit dislocation growth mode on highly lattice-mismatched InxGa1-xSb epilayer grown on GaAs substrate by metalorganic chemical vapor deposition (original) (raw)
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Nanoscale research …, 2009
We report structural analysis of completely relaxed GaSb epitaxial layers deposited monolithically on GaAs substrates using interfacial misfit (IMF) array growth mode. Unlike the traditional tetragonal distortion approach, strain due to the lattice mismatch is spontaneously relieved at the heterointerface in this growth. The complete and instantaneous strain relief at the GaSb/GaAs interface is achieved by the formation of a two-dimensional Lomer dislocation network comprising of pure-edge (90°) dislocations along both [110] and [1-10]. In the present analysis, structural properties of GaSb deposited using both IMF and non-IMF growths are compared. Moiré fringe patterns along with X-ray diffraction measure the long-range uniformity and strain relaxation of the IMF samples. The proof for the existence of the IMF array and low threading dislocation density is provided with the help of transmission electron micrographs for the GaSb epitaxial layer. Our results indicate that the IMF-grown GaSb is completely (98.5%) relaxed with very low density of threading dislocations (105 cm−2), while GaSb deposited using non-IMF growth is compressively strained and has a higher average density of threading dislocations (>109 cm−2).
Crystals
We report on the role of AlSb material in the reduction of threading dislocation density (TDD) in the GaSb/AlSb/GaAs system. The AlSb layers were grown using low-temperature (LT) MBE, exploiting the interfacial misfit (IMF) dislocation array. AlSb layers with four different thicknesses in the range of 1–30 nm were investigated. The results showed the inhibiting role of LT-AlSb layers in the reduction of TDD. Values of TDD as low as 2.2 × 106 and 6.3 × 106 cm−2 for samples with thin and thick AlSb layers were obtained, respectively. The filtering role of AlSb material was proven despite the IMF-AlSb/GaAs interface’s imperfectness caused by the disturbance of a 90° dislocation periodic array by, most likely, 60° dislocations. The dislocation lines confined to the region of AlSb material were visible in HRTEM images. The highest crystal quality and smoother surface of 1.0 μm GaSb material were obtained using 9 nm thick AlSb interlayer. Unexpectedly, the comparative analysis of the resu...
2019
GaSb based photovoltaic devices have been demonstrated on GaAs substrates by an inducing interfacial array of 90° misfit dislocations. Despite the beneficial qualities of the highly stable 90° misfit dislocation, there is a significant density of residual threading dislocations in the GaSb layer, resulting in the degradation of the electrical performance of such photovoltaic cells compared to lattice matched devices. We aim to reduce threading dislocation density by optimizing growth temperature and by using an AlSb dislocation filtering layer. The growth temperature optimization results in a reduction of the threading dislocation density to 1.3 × 10 cm. Adding an AlSb dislocation filtering layer further improves the electrical performance of the GaSb solar cells by reducing the threading dislocation density to 4 × 10 cm. A comparison between the experimental data and theoretical calculation confirms that the recombination in dislocation centers is a dominant loss mechanism in GaSb ...
Journal of Materials Science: Materials in Electronics, 2016
Strain-relieved GaSb quantum dots on GaAs can be achieved by either periodic interfacial misfit (IMF) or the conventional Stranski-Krastanov (SK) growth modes by changing the growth parameters. In this study, the Sb interfacial treatment was employed to improve the GaSb crystal quality including low defect density, smooth surface morphology, and high hole mobility. This technique yields two-dimensional (2D) islands with a height as low as 1.7 nm and width up to 190 nm in the IMF growth mode. In contrast to the interfacial treatments conventionally employed in the initial strain relaxation of GaSb/GaAs hererostructure, the Sb treatment promotes the formation of strong Ga-Sb bonds on the surface of the grown island, which effectively reduces the interfacial free energy and thus promotes the formation of 2D islands. With the Sb interfacial treatment, a high-relaxation 100-nm GaSb epilayer was grown on the GaAs substrate, the epilayers was strain relaxed and exhibited enhanced electrical properties with a high hole mobility of *667 cm 2 V-1 s-1 and with superior optical properties as evidenced by the photoluminescence B-line peak. The results of this study demonstrate an effective interfacial-treatment growth technique to relax the initial strain for the highly mismatched GaSb layers grown on a GaAs substrate.
A strain relief mode at interface of GaSb/GaAs grown by metalorganic chemical vapor deposition
Applied Physics Letters, 2011
Epitaxial growth of Ti3SiC2 thin films with basal planes parallel or orthogonal to the surface on α-SiC Appl. Phys. Lett. 101, 021606 (2012) Recombination mechanisms in heteroepitaxial non-polar InGaN/GaN quantum wells J. Appl. Phys. 112, 013534 (2012) Growth and characterizations of semipolar (112) InN J. Appl. Phys. 112, 013530 Epitaxial two dimensional aluminum films on silicon (111) by ultra-fast thermal deposition J. Appl. Phys. 111, 124320 Atomic behavior of carbon atoms on a Si removed 3C-SiC (111) surface during the early stage of epitaxial graphene growth
Dislocation-free InSb grown on GaAs compliant universal substrates
Applied Physics Letters, 1997
An innovative compliant GaAs substrate was formed by wafer bonding a 30 Å GaAs layer to a bulk GaAs crystal with a large angular misalignment inserted about their common normals. InSb epitaxial layers, which is about 15% lattice mismatched to GaAs, have been grown on both compliant substrates and conventional GaAs substrates. Transmission electron microscopy studies showed that the InSb films grown on the compliant substrates have no measurable threading dislocations, whereas the InSb films on the conventional GaAs substrates exhibited dislocation densities as high as 10 11 cm Ϫ2. The observations made here suggest that the defect-free heteroepitaxial growth of exceedingly large lattice-mismatched crystals can be achieved with compliant universal substrates.
Reduction of dislocation density by thermal annealing for GaAs/GaSb/Si heterostructure
Journal of Crystal Growth, 1995
This paper describes the reduction of dislocation density in molecular beam epitaxy (MBE)-grown GaAs on Si with GaSb intermediate layer by thermal cycle annealing (TCA). The effects of the annealing temperature on the crystal quality of the top GaAs layer on Si are discussed by using of results of the etch pit density and transmission electron microscopy images. An etch pit density (EPD) of the top GaAs layer as low as 8.5 X lo6 cm-' has been obtained when the maximum annealing temperature was 9OO"C, which is higher than the melting point of the intermediate GaSb layer.
Dislocations in medium to highly mismatched III–V epitaxial heterostructures
Journal of Crystal Growth, 1993
Strain induced dislocations have been studied in medium mismatched In~Ga 1 _~As/GaAssingle layers (0.57% <f < 1.07%) and superlattice heterostructures (0.43% <f <2.1%) and highly mismatched (f 3.8%) InP/GaAs single layers. The location, propagation and nature of misfit dislocations have been investigated using electron microscopy techniques. The InGaAs/GaAs single layers were grown with different compositions and thicknesses directly onto the GaAs substrate without any GaAs buffer layers. In this case misfit dislocations were found to be confined at the heterointerface or within 150-200 nm of the interface, mostly inside the epilayer. On the contrary, a GaAs buffer layer was grown between the superlattice structures and the substrates. For 0.43% <f < 1.35 misfit dislocations were confined inside the buffer layers or at the buffer-superlattice interface, without threading the superlattice. For higher mismatch values (f= 2.1%), the superlattice presented both interfacial and threading dislocations. Asymmetric dislocation movement induced by the electron beam in a scanning electron microscope on as-grown samples, most likely associated with metastahility of the superlattices, was observed when thickness and composition were such that a low linear dislocation density (< 2x l0~cm') was present. Mainly 60°type misfit dislocations were observed in all the lnGaAs/GaAs structures investigated. The InP/GaAs heterostructures had a higher linear dislocation density (= 106 cm 1) and planar defects were found to thread the epilayers from the heterointerface up to the free surface. The density of these defects was found to decrease as the free surface was approached. Both 60°and 90°type dislocations were found in this system.
Misfit dislocation reduction in InGaAs epilayers grown on porous GaAs substrates
Applied Surface Science, 2014
Elastic accommodation of heteroepitaxial layers beyond their critical thickness is crucial for the reduction of misfit dislocations. One approach is to utilize substrate engineering in order to delay plastic relaxation. In this work, pore networks were introduced electrochemically in GaAs substrates in order to modify their mechanical responses. In x Ga 1−x As epilayers with nominal indium contents up to x = 0.20 were then deposited by MOVPE, and were compared to similar epilayers grown on nonporous GaAs. Strain relaxation and defect introduction were studied by TEM observations, x-ray diffraction, and photoluminescence measurements. It was found that the porous substrates acted to reduce the density of misfit dislocations, thereby increasing the epilayer critical thickness. The InGaAs epilayers retained a significantly higher amount of elastic strain compared to ones grown on nonporous GaAs. The onset of plasticity was mediated by the pores, which acted as nucleation sites for 60 • dislocations that glided toward the interface.