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In this study, the correlation between the Emission Microscopy (Em.Mi.) related to the failure site of the 4H-SiC 650V MOSFET devices after reliability test and epitaxial dislocation defects is presented. Devices failed at the High-Temperature Reverse Bias (HTRB) test were considered. Device layers have been stripped out by chemical wet etching and etched in a high temperature KOH solution to characterize defects emerging at the SiC surface. This approach was used to correlate failure emission spots with underlying structure of the material. KOH etching process on delayered devices was performed at 500°C for 10 minutes and then analysis by optical microscopy and SEM was carried out for defect classification and correlation with failure location.

We present the results of a transmission electron microscopy and X-ray diffractometry investigation of AlN/c-Al2O3 templates with GaN ultrathin insertions grown by plasma-assisted molecular beam epitaxy. It has been shown that AlN buffer layers with faceted surface morphology provide a greater threading dislocation density reduction than smooth layers. The filtering effect of GaN ultrathin insertions has been confirmed.

Accepted: 2021-10-05, PA2210048000

X-ray topography defect analysis of entire 1.8-inch GaN substrates, using the Borrmann effect, is presented in this paper. The GaN wafers were grown by the ammonothermal method. Borrmann effect topography of anomalous transmission could be applied due to the low defect density of the substrates. It was possible to trace the process and growth history of the GaN crystals in detail from their defect pattern imaged. Microscopic defects such as threading dislocations, but also macroscopic defects, for example dislocation clusters due to preparation insufficiency, traces of facet formation, growth bands, dislocation walls and dislocation bundles, were detected. Influences of seed crystal preparation and process parameters of crystal growth on the formation of the defects are discussed.

In this study, the improvement of reverse leakage current characteristics with a sputtered (SP) -AlN buffer layer in GaInN-based green light-emitting diodes (LEDs) has been presented for the first time. To understand the origin of the improvement, a detailed review and careful analysis of reverse leakage current characteristics were performed. The review and analysis identified that the improvement was primarily caused by the suppression of variable-range-hopping process obtained by replacing conventional low-temperature GaN buffer. Verification that threading dislocations and V- defects can enhance the variable-range-hopping process has been received. We believe that this study will contribute to the realization of green LEDs with advantages of high reliability, a long lifetime, and electrical robustness.

The performance of X-ray imaging detectors based on epitaxial Ge-crystal arrays grown on patterned Si substrates is severely limited by the presence of misfit and threading dislocations. Here, we study the effect of cyclic thermal annealing on misfit dislocations at the Ge/Si interface. By scanning transmission electron microscopy and energy dispersive X-ray spectroscopy, it is shown that the annealing process promotes the diffusion of Si into the Ge crystal resulting in a corrugated interface and slightly reduces the dislocation density. Finally, our results demonstrate that the thermal process is very effective at eliminating twin boundaries.

We present principle of defect characterization of GaN using multiphoton-excitation photoluminescence and several experimental results. Threading dislocations and basal plane dislocations in n-type GaN are observed from near-band-edge emission imaging. The diameters of dark spots and dark lines are determined by the minority carrier diffusion length. Three-dimensional feature of dark lines is different by the Burgers vectors of dislocations. Based on these properties, nondestructive classification of dislocations is possible. Simultaneous detection of near-band-edge emission and yellow luminescence can be utilized to visualize three-dimensional growth processes such as facet-initiated epitaxial lateral overgrowth, which is used to obtain GaN substrates with low threading dislocation densities.

Atom probe tomography (APT) provides the three-dimensional imaging of materials and their compositional information at atomic-scale resolution. However, various factors such as the limited volume and/or the imperfect detection efficiency sometimes make it difficult to fully understand a material only by APT. The combination of APT with scanning transmission electron microscopy (STEM) in GaN-based systems allows more reliable information of complex problems such as magnesium (Mg) segregations in extended defects or indium (In) fluctuations in multiple quantum wells. The combined analyses have revealed that Mg atoms in GaN are likely to be segregated in polarity inversion domains formed through post-implantation annealing. This combinational approach also provided a direct evidence of Mg atoms diffusing along threading dislocations in the p-n junction of GaN; such information is useful to understand the mechanism of leakage current in the junction. Combined use of APT and STEM also revealed the existence of In clusters and compositional fluctuations in InGaN/GaN multiple quantum wells, which can be used to understand carrier localization in these system. This chapter reviews the remarkable achievements obtained via combined APT and STEM analyses in GaN based materials and devices, and discusses the future outlook.

The use promising group III-V materials for photovoltaic applications is hindered by the high density of threading dislocations when integrated with silicon technology. Here, we present an electrochemical deep etching strategy to drastically reduce the defect density. We seek to accommodate the effects of the lattice mismatch by introducing nanovoids inside the Ge/Si interface, which intercept dislocations, facilitating their subsequent annihilation and prevent them from reaching the active layers of the device. This allows an appreciable dislocation density, which unlocks the potential of providing high quality Ge-on-Si virtual substrates for growing lattice-matched III-V photovoltaics.

A mechanism of controlling the degree of strain relaxation in GeSn epilayers, grown by molecular beam epitaxy on Ge/Si(001) substrates, is reported in this work. It is demonstrated that by suitably controlling the thickness and the growth recipe of the underlying Ge buffer layer, both fully-strained and highly-relaxed GeSn epilayers can be obtained, without significant Sn segregation. The strain relaxation of the GeSn epilayer is mediated by threading dislocations of the Ge buffer layer, propagating across the Ge-GeSn interface. Systematic estimation of the threading dislocation density in both the alloy epilayer and the Ge buffer layer, by the approach developed by Benediktovich et al. [A. Benediktovitch, A. Zhylik, T. Ulyanenkova, M. Myronov, A. Ulyanenkov (2015), J. Appl. Cryst. 48, 655–665] supports this observation, and also reveals that no additional dislocations are generated at the Ge-GeSn interface. Together with recently reported techniques to arrest dislocation propagation in GeSn epilayers, these results bode extremely well for realization of highly-relaxed GeSn epilayers, much coveted for development of GeSn-based emitters.

Compositionally step-graded Al1-xInxAs (x = 0–0.31) and Ga1-xInxP (x = 0.48–0.78) metamorphic buffers were grown on GaAs substrates by metal-organic chemical vapor deposition to fulfill the lattice transition from GaAs to In0.30Ga0.70As.With the same buffer structure, thickness, and misfit grade rate, InGaAs layers on AlInAs buffer displayed a much better surface morphology and lower density threading dislocations than that on GaInP buffer. The reciprocal space mappings of the samples displayed that the AlInAs buffer relax the strain quickly, while the GaInP buffer remained partially strained through the layers and sufficient relaxation was achieved after the InGaAs layer growth. The different strain relaxation mechanisms were mainly attributed to the high growth temperature of AlInAs, which facilitate dislocation nucleation and glide, especially α dislocations. For GaInP buffers, the quality can be improved profoundly by reducing the misfit grade rate. This work provides a helpful guide for the design and growth of lattice mismatched semiconductor devices.

Three InGaN/GaN multi-quantum well (MQW) samples are grown on c-plane sapphire substrate and free standing GaN substrate, respectively. The emission and structural sproperties of these samples are studied in detail. It is found that the thermal stability and emission homogeneity of InGaN/GaN MQWs grown on GaN substrate is much better than that grown on sapphire substrate. This may be attributed to the lower density of threading dislocations in InGaN/GaN MQW regions grown on GaN substrate. Threading dislocations often end with V-pits at InGaN surface, and often contain In-rich clusters around them. These In-rich regions are easy to segregate during high temperature p-type layer growth, leading to the degradation of InGaN/GaN MQWs ultimately.

The defect structure of a thick (~15 μm) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.

GaSb based photovoltaic devices have been demonstrated on GaAs substrates by 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 × 108 cm−2. Adding an AlSb dislocation filtering layer further improves the electrical performance of the GaSb solar cells by reducing the threading dislocation density to 4 × 107 cm−2. A comparison between the experimental data and theoretical calculation confirms that the recombination in dislocation centers is a dominant loss mechanism in GaSb solar cell grown on GaAs substrate.

High quality In0.30Ga0.70As layers on GaAs substrates were obtained using compositional undulating step-graded Ga1-xInxP (x = 0.48–0.78) buffers grown by metal-organic chemical vapor deposition. The density of threading dislocation is about 4.0 × 106 cm−2 and the root-mean-square roughness is only 5.20 nm, which is much better than those grown on the conventional step-graded metamorphic buffer. On one hand, the reversed GaInP layers reduce the distribution imbalance of α dislocations between the (1 1 1) and (−1 −1 1) slip planes, which promote dislocation glide. On the other hand, the inserted tensile strained GaInP layers change the direction of dislocation glide and facilitate dislocation annihilations, which effectively confine the threading dislocations in the buffer. Overall, this work provides a promising way to obtain virtual substrates for the achievement of desired metamorphic devices.

The influence of dislocation filters based on low-temperature layers (LT) of GaAs and postgrowth annealing on the perfection of GaAs/Si heterostructures is discussed. It is shown that LT-GaAs layers reduce the density of threading dislocations and surface roughness. Post-growth annealing at a temperature of 650 °C reduces the concentration of nonradiative recombination centers in GaAs/Si layers to a level close to the level in GaAs layers grown on a matched substrate.

Threading dislocations in a heteroepitaxial α-Ga2O3 film was visualized as etch pits on the surface. We found that etch pits were formed on a c-plane α-Ga2O3 epilayer by HCl gas etching. The epilayer was prepared by using epitaxial lateral overgrowth technique with a stripe mask pattern. The etch pit density was very high in the window region, and much lower in the laterally grown area on the mask. A line of etch pits was observed at a coalesced boundary. Thus, the etch pit density had a clear correlation with the dislocation density. The correspondence between the etch pits and dislocations was confirmed by cross-sectional bright- and dark-field transmission electron microscopy (TEM). This gas-etching technique can clarify the distribution of dislocations in a wide area, which cannot be explored effectively by TEM.

Threading dislocations in c-plane (Al,Ga)N layers are surrounded by areas with reduced light generation efficiency, called “dark spots.” These areas are observable in luminescence measurements with spatial resolution in the submicrometer range. Dark spots reduce the internal quantum efficiency in single layers and light-emitting devices. In cathodoluminescence measurements, the diameter of dark spots (full width at half maximum [FWHM]) is observed to be 200–250 nm for GaN. It decreases by 30–60% for AlxGa1−xN with x ≈ 0.5. Furthermore, the dark spot diameter increases with increasing temperature from 83 to 300 K in AlGaN, whereas it decreases in GaN. Emission energy mappings around dark spots become less smooth and show sharper features on submicrometer scales at low temperature for AlGaN and, on the contrary, at high temperature for GaN. It is concluded that charge carrier localization dominates the temperature dependence of dark spot diameters and of the emission energy distribution around threading dislocations in AlGaN, whereas the temperature-dependent excitation volume in cathodoluminescence and charge carrier diffusion limited by phonon scattering are the dominant effects in GaN. Consequently, with increasing temperature, nonradiative recombination related to threading dislocations extends to wider regions in AlGaN, whereas it becomes spatially limited in GaN.

The role of the Al 0.2 Ga 0.8 N/Al 0.4 Ga 0.6 N superlattice (SL) and AlN/GaN SL on the strain engineering of GaN films on Si (111) is investigated. From Raman scattering measurements, a satellite E2 peak of GaN is observed in the sample with AlN/GaN SL. It is also found the AlN/GaN SL buffer have a better effect at the blocking of threading dislocations (TDs) while lots of dislocations annihilate at the interface of Al 0.2 Ga 0.8 N/Al 0.4 Ga 0.6 N SL and GaN. In the GaN films, TDs bend and interact with each other, leading to the relaxation of compressive stress in GaN films. The relaxation rate of compressive stress in GaN films with different SL structures is studied.

A hendecafacet (HF) microsized light emitter based on an InGaN/GaN multiple quantum well (MQW) is grown via selective area metal–organic chemical vapor deposition. The HF microsized light emitter is found to possess four crystallographic facets, (0001), {1101}, {1122}, and {11–20}. Distinct facet-dependent emission properties, investigated by confocal scanning photoluminescence (PL) and cathodoluminescence (CL) measurements, are found to originate from differences in indium composition and InGaN quantum well thickness of the MQW. Facet-dependent recombination properties, examined by temperature-dependent micro-PL and PL streak images, suggest that the localization energy and nonradiative recombination of carriers at MQW on each facet are varied with the polarization fields and threading dislocations. Besides, scanning time-resolved PL measurements reveal that the recombination lifetime around the edge where different facets meet is shorter than that in the facet regions, implying such nonradiative recom...

We report the influences of a Si-doped graded-superlattice (SiGSL) on the structural, optical, and electrical properties of InGaN/GaN light-emitting diodes (LEDs). For comparison, LEDs fabricated on an undoped graded superlattice (unGSL-LED) and conventional LEDs without the superlattice (C-LED) were prepared. The dependences of the carrier behaviors on the surface inhomogeneity and the defect/dislocation distribution were investigated by using fluorescence microscopy images, wherein the dark features corresponding to the defects/threading dislocations for the unGSL-LED and the SiGSL-LED were significantly reduced compared to that for the C-LED. The photoluminescence intensities of the unGSL-LED and the SiGSL-LED were 1.15 and 1.24 times stronger than that of the C-LED, respectively. The output powers of the unGSL-LED and the SiGSL-LED at an injection current of 20 mA were measured to be 1.32 and 1.41 times higher than that of the C-LED, respectively. Moreover, the electrostatic discharge characteristics of the LED sample using the SiGSL structure were drastically improved.

In this work, a novel strategy for high-quality AlN templates epitaxy on sapphire substrates with sputtered buffer layers combined with a low- and high-temperature alteration technique is proposed. The best full width at half maximum values for (0002) and (1 1 ¯ 02) reflections are 207 and 377 arcsec, respectively. Investigations indicate the joint effect of growth mode control and sputtered buffer layer results in the improvement of AlN crystalline quality. Firstly, threading dislocations density can be significantly decreased due to the alteration from three-dimensional to two-dimensional growth mode. Moreover, the graded composition of AlON layer in the sputtered buffer layer is believed to alleviate lattice mismatch between sapphire substrates and AlN, which also contributes to low dislocations density in AlN templates.

In this work GaN films are grown on 4H-SiC substrates with different surface terrace step width and the influence of the step width on the crystal quality of GaN is studied using X-ray diffraction (XRD) method. The results prove that the different surface terrace step width has a big impact on the (0 0 2) and (1 0 2) full width at half maximum (FWHM) of GaN films. It is mainly because the nucleation and coalescence mechanism of AlN is closely related with the surface step width, resulting in different densities of threading dislocations in the subsequent grown GaN films.

Correspondence between threading dislocations (TDs) in epitaxial films and the etch pits observed upon selective chemical etching of the samples was studied in Ge/Si(001) heterostructures. It is established that the density of TDs revealed in epitaxial films with thicknesses h ≤ 1 μm can be significantly understated because of insufficient resolution of optical microscopy. Recommendations are given that increase the reliability of PD density estimation by means of structure-sensitive etching.

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We present an investigation of the edge and screw threading dislocation densities in GaN- heteroepitaxial layers with different thicknesses grown on sapphire substrate using X-ray diffraction. Taking into account the finite penetration depth nature of the X-rays, we obtained depth profiles of threading dislocations along the layer thickness and attributed the observed features with annihilation centers.

Recently there has been renewed interest in resonant tunnel diodes (RTD) owing to the demonstration of repeatable room temperature negative differential resistance (RT-NDR) [1], [2] and high peak current densities [3] in GaN-based RTDs. While most of the successful demonstrations of RT-NDR have been from device structures grown on low dislocation-density, freestanding (FS) GaN substrates, there have been a few reports of repeatable RT-NDR from GaN-based RTDs grown on GaN templates on sapphire [4], [5], which have significantly higher densities of threading dislocations (TDs) than FS GaN substrates, but much lower cost. Furthermore, due to the large spontaneous and piezoelectric charge found at the heterointerfaces in III-nitrides, GaN-based RTDs, such as the one illustrated in Fig. 1(a), have highly unusual energy band diagrams, even at 0V bias [Fig. 1(b)]. However, observations of RT-NDR in GaN RTDs on GaN templated sapphire substrates have been restricted to devices of very small active area, typically less than $10\ \mu \mathrm{m}^{2}$ [4], [5].

The GaInAsSb material has been conventionally grown on lattice-matched GaSb substrates. In this work, we transplanted this material onto the GaAs substrates in molecular beam epitaxy (MBE). The threading dislocations (TDs) originating from the large lattice mismatch were efficiently suppressed by a novel metamorphic buffer layer design, which included the interfacial misfit (IMF) arrays at the GaSb/GaAs interface and strained GaInSb/GaSb multi-quantum wells (MQWs) acting as dislocation filtering layers (DFLs). Cross-sectional transmission electron microscopy (TEM) images revealed that a large part of the dislocations was bonded on the GaAs/GaSb interface due to the IMF arrays, and the four repetitions of the DFL regions can block most of the remaining threading dislocations. Etch pit density (EPD) measurements indicated that the dislocation density in the GaInAsSb material on top of the buffer layer was reduced to the order of 106 /cm2, which was among the lowest for this compound material grown on GaAs. The light emitting diodes (LEDs) based on the GaInAsSb P-N structures on GaAs exhibited strong electro-luminescence (EL) in the 2.0&ndash, 2.5 &micro, m range. The successful metamorphic growth of GaInAsSb on GaAs with low dislocation densities paved the way for the integration of various GaInAsSb based light emitting devices on the more cost-effective GaAs platform.

We have investigated the interaction between carbon impurities and threading dislocations and their impact on the transport properties of GaN grown on Si substrates. The incorporation of carbon impurity was found to be associated with dislocation density, with a linear dependence. It indicates that the carbon may accumulate around the dislocations. The temperature-dependent Hall-effect measurement further confirmed that those carbon-decorated dislocations can act as acceptor-like traps, existing at every c-lattice spacing along a threading dislocation. The acceptor-like traps are important scattering centers and, thus, cannot be neglected. By reducing the density of the carbon-decorated dislocation via introducing a thick dislocation filtering layer to reduce the dislocation-related acceptor-like trap scattering, a record room-temperature electron mobility of 1090 cm2/V s with a carrier concentration of ∼2 × 1016 cm−3 for n--GaN on Si was achieved. Our results provide an effective approach to obtain high-quality n−-GaN on Si for vertical GaN based devices.

Burgers vectors b of threading dislocations in freestanding GaN substrates were identified through statistical classification using the etch pit and multiphoton-excitation photoluminescence methods. The b = 1a + 1c threading mixed dislocations were propagated with large inclination angles more than four degrees from the c-axis to minimize elastic strain energy. The b = 1c threading edge dislocations had a large contrast difference of more than 0.4 in the photoluminescence image due to their strong nonradiative properties. Based on these characteristics obtained through multiphoton-excitation photoluminescence measurements, major types of dislocations (b = 1a, 1a + 1c, 1c) could statistically be identified.

We have systematically investigated highly mismatched AlInSb photodiodes grown on GaAs substrates operating in the mid-infrared range. A novel characterization method was introduced to analyze the recombination mechanism within an active layer of the devices, which revealed a high conductance stemming from the leaky behavior of dislocations. The introduction of a dislocation filter layer successfully reduced threading dislocations and improved resistance area product of photodiodes, leading to high detectivity at room temperature.

Threading dislocations have been studied by means of etch pit method using molten KOH + Na 2 O 2 solution, cathodoluminescence and transmission electron microscopy. We focus on the geometrical features of etch pits and their correlation with the recombination behavior at the dislocations. Four types of etch pits can be recognized after etching according to their sizes and depths, among which the middle-sized etch pits correspond to dislocations with the strongest non-radiative recombination. TEM observation has confirmed that dislocation beneath the large-sized etch pit is a mixed-type dislocation having both c - and a -component.

High-resistance GaN with low dislocation density adopting growth mode modification has been investigated by metalorganic chemical vapor deposition. The sheet resistance of the order of 1016 Ω/sq has been achieved at room temperature by diminishing the oxygen impurity level close to the substrate with an AlN blocking layer. Attributed to this method which offers more freedom to tailor the growth mode, a three-dimensional (3D) growth process is introduced by adjusting the growth pressure and temperature at the initial stage of the GaN epitaxy to improve the crystalline quality. The large 3D GaN grains formed during this period roughen the surface, and the following coalescence of the GaN grains causes threading dislocations bending, which finally remarkably reduces the dislocation density.

A TEM study of defect structure of GaN films grown by chloride vapor-phase epitaxy (HVPE) on GaN/Al 2 O 3 substrates was performed. The substrates were fabricated by metal-organic chemical vapor deposition overgrowth of templates with buried column pattern. The results of TEM study showed that the character of the defect structure of HVPE-grown films was determined by the configuration of the column pattern in the substrate. By choosing the proper pattern, the reduction in the density of threading dislocations in the films by two orders of magnitude (in respect to the substrate material), down to the value of 10 7 cm −2 , was achieved.

In-situ etching of GaAs with CBr 4 in metalorganic vapor phase epitaxy has been investigated at different temperatures using in-situ reflectivity to measure the etch rates. Deep (150 nm) etching of epitaxially-grown GaAs leads to the development of etch pits on the surface, corresponding to the emerging points of threading dislocations. Addition of trimethylgallium (TMGa) leads to a linear superposition of growth and etching. Trimethylaluminium (TMAl) added in moderate quantity enhances the etch rate and inhibits the development of etch pits. A model description for the enhanced etch rate is presented.

The morphology of GaN-on-GaN vertical p-i-n diode devices after reverse-bias electrical stressing to breakdown has been investigated. All failed devices had irreversible structural damage, showing large surface craters that were ∼15–35 μm deep with lengthy surface cracks. Cross-sectional electron micrographs of failed devices showed substantial concentrations of threading dislocations around the cracks and near the crater surfaces. Progressive ion-milling across damaged devices revealed high densities of threading dislocations and the presence of voids beneath the surface cracks; these features were not observed in any unstressed devices. These results should serve as a useful reference for future reliability studies of vertical high-power GaN devices.

We obtained a high-quality 40-pair AlInN/GaN distributed Bragg reflector with a high growth rate of the AlInN layers (500 nm h−1), showing almost no threading dislocations and a peak reflectivity of 99.9% at 413 nm, by using a 0.3 nm GaN cap layer grown on the AlInN layer at low growth temperature. We also found that the threading dislocations generated at the interfaces between the bottom AlInN and the top GaN in the cases of 5–10 nm GaN cap layers which were typically used. Excess In atoms on the AlInN surfaces seem to cause the generation of the threading dislocations.

AlN/GaN double-barrier resonant tunnel diodes have been grown by rf-plasma assisted molecular beam epitaxy at temperatures between 760 and 860 °C on metalorganic chemical vapor deposition-grown GaN templates with sapphire substrates. Room temperature negative differential resistance (NDR) was observed for all samples despite the presence of higher densities of threading dislocations in the device layers than in the MOCVD GaN template. The fraction of devices exhibiting NDR and the peak-to-valley current ratio was small for each sample (typically 1%–10% and 1.003–1.1, respectively). A clear trend of increasing peak current density with increasing growth temperature was observed.

SiGe films were grown on a chemical vapor deposition (CVD)-grown Si0.88Ge0.12/Si (0 0 1) graded film with different growth solution compositions using a temperature interval of 950-940 °C by liquid phase epitaxy (LPE). The LPE films grown on the CVD-grown SiGe/Si (0 0 1) graded film are ≥86% relaxed, much more relaxed than those on bare Si (Wang and Quitoriano, 2019) since the existing threading dislocations in the CVD-grown SiGe/Si (0 0 1) graded film glide to create misfit dislocations without needing to nucleate new ones. The threading dislocation density of the LPE films is slightly lower than that of the CVD-grown SiGe films and on the same order of magnitude, ~106 cm−2. Since the CVD-grown SiGe/Si (0 0 1) graded film was annealed for 4 h before the LPE growth occurred, the properties of the CVD-grown SiGe/Si (0 0 1) graded film were studied and we found that the CVD-grown SiGe/Si (0 0 1) graded film have SiGe islands appear all over the surface aligned along the 〈1 1 0〉 crosshatch morphology and become more relaxed after annealing.

We report reducing the density of threading dislocations (TDs) in stacking-fault-free semipolar (20 2 ¯ 1 ) GaN grown on sapphire by inserting an AlGaN/GaN superlattice (SL). We have studied the influence of AlGaN/GaN SL on the reduction of TDs and found that the density of TDs decreases by more than a factor of three with increasing the number of AlGaN/GaN SL pairs up to 10. Furthermore, blue light emitting diodes (LEDs) have been grown on semipolar (20 2 ¯ 1 ) GaN/sapphire templates with inserted 10 pairs of AlGaN/GaN SL showing doubled light output power in comparison with the LEDs grown without AlGaN/GaN SL.

Since the invention of dislocation sidewall gettering (DSG) in 2000 the technique has been applied extensively in infrared focal-plane arrays and flat-panel displays. However, development of DSG technology has been guided mostly by empirical trials due to the lack of detailed physical models. Here we demonstrate the application of a dislocation dynamics model to evaluate DSG approaches in both ZnSySe1-y/GaAs (001) and InGaxAs1-x/GaAs (001) heterostructures. We find that the effectiveness of DSG is strongly dependent on composition in both material systems.

An overview is given on how to tackle the question of the electrical activity of extended defects which are inevitably present in hetero-epitaxial III-V layers on silicon. Analysis methods are described which rely on simple device structures containing a specific type of extended defect (here, threading dislocations). Applying the same methods to real scaled FinFETs is rather challenging. Instead Generation-Recombination noise spectroscopy provides data that can be compared with other more standard techniques, like Deep-Level Transient Spectroscopy (DLTS) in order to identify the presence of an electrically active extended defect in the channel material.