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Purpose Glioma patients, especially recurrent glioma, suffer from a poor prognosis. While advances to classify glioma on a molecular level improved prognostication at initial diagnosis, markers to prognosticate survival in the recurrent situation are still needed. As 18 kDa translocator protein (TSPO) was previously reported to be associated with aggressive histopathological glioma features, we correlated the TSPO positron emission tomography (PET) signal using [18F]GE180 in a large cohort of recurrent glioma patients with their clinical outcome. Methods In patients with [18F]GE180 PET at glioma recurrence, [18F]GE180 PET parameters (e.g., SUVmax) as well as other imaging features (e.g., MRI volume, [18F]FET PET parameters when available) were evaluated together with patient characteristics (age, sex, Karnofsky-Performance score) and neuropathological features (e.g. WHO 2021 grade, IDH-mutation status). Uni- and multivariate Cox regression and Kaplan–Meier survival analyses were performed to identify prognostic factors for post-recurrence survival (PRS) and time to treatment failure (TTF). Results Eighty-eight consecutive patients were evaluated. TSPO tracer uptake correlated with tumor grade at recurrence (p IDH-wild-type versus IDH-mutant tumors. Within the subgroup of IDH-mutant glioma (n = 46), patients with low SUVmax (median split, ≤ 1.60) had a significantly longer PRS (median 41.6 vs. 25.3 months, p = 0.031) and TTF (32.2 vs 8.7 months, p = 0.001). Also among IDH-wild-type glioblastoma (n = 42), patients with low SUVmax (≤ 1.89) had a significantly longer PRS (median not reached vs 8.2 months, p = 0.002). SUVmax remained an independent prognostic factor for PRS in the multivariate analysis including CNS WHO 2021 grade, IDH status, and age. Tumor volume defined by [18F]FET PET or contrast-enhanced MRI correlated weakly with TSPO tracer uptake. Treatment regimen did not differ among the median split subgroups. Conclusion Our data suggest that TSPO PET using [18F]GE180 can help to prognosticate recurrent glioma patients even among homogeneous molecular subgroups and may therefore serve as valuable non-invasive biomarker for individualized patient management. Graphical abstract

β-amyloid (Aβ) and tau aggregation as well as neuronal injury and atrophy (ATN) are the major hallmarks of Alzheimer’s disease (AD), and biomarkers for these hallmarks have been linked to neuroinflammation. However, the detailed regional associations of these biomarkers with microglial activation in individual patients remain to be elucidated.We investigated a cohort of 55 patients with AD and primary tauopathies and 10 healthy controls that underwent TSPO-, A-, tau-, and perfusion-surrogate-PET, as well as structural MRI. Z-score deviations for 246 brain regions were calculated and biomarker contributions of Aβ (A), tau (T), perfusion (N1) and gray matter atrophy (N2) to microglial activation (TSPO, I) were calculated for each individual subject. Individual ATN-related microglial activation was correlated with clinical performance and CSF soluble TREM2 (sTREM2) concentrations.In typical and atypical AD, regional tau was stronger and more frequently associated with microglial activation when compared to regional A (AD: βT= 0.412±0.196 vs. βA= 0.142±0.123, p < 0.001; AD-CBS: βT= 0.385±0.176 vs. βA= 0.131±0.186, p = 0.031). The strong association between regional tau and microglia reproduced well in primary tauopathies (βT= 0.418±0.154). Stronger individual associations between tau and microglial activation were associated with poorer clinical performance. In patients with 4RT, sTREM2 levels showed a positive association with tau-related microglial activation.Tau pathology has strong regional associations with microglial activation in primary and secondary tauopathies. An index of tau- and Aβ-associated microglia activation accounts for regional heterogeneity and allows for clinical and biomarker correlations with ATN-specific neuroinflammation.

The purpose of this study was to determine whether different types of position-related cranial deformities show changes after completion of head orthosis therapy. We investigated how children's age at the begin of molding helmet therapy affects the duration and long-term stability of treatment. In addition, parental satisfaction with helmet therapy has been investigated.Between 2012 and 2019, 47 patients have been analyzed after undergoing helmet therapy. At the beginning of treatment different disease pattern were classified. Posterior deformational Plagiocephalus defined by a cranial vault index (CVA)1 cm and a cranial index (CI) ≤ 90%. Posterior deformational Brachycephalus defined by CVA ≤ 1 cm and CI90%. Posterior deformational combined Plagio- and Brachycephalus defined by CVA1 cm and CI90%. At the beginning of therapy, the end of therapy and within 5-year-follow-up CI and CVA was measured by three-dimensional photogrammetry for 2 age groups (4-6 and 7-12 months). Additionally, parents completed a standardized questionnaire to evaluate the personal assessment of treatment outcome.During treatment CI and CVA of all children decreased significantly (P 0.001). Furthermore, CI significantly decreased after ending helmet therapy (P 0.001). Cranial vault index decreased not significantly in the same period (P = 0.361). For the 4 to 6 months old group treatment time was significantly shorter than for the older group. Before starting helmet therapy nearly half of the parents graded the scull as moderate and one-third as severe deformed. After ending treatment, the majority of parents report satisfaction and compliance. However, one-third of parents noted a slight scull deformation and personal load during therapy.After completion of therapy an improvement of head shape can be expected for the majority of children. This is particularly evident for improvement of the CI and a shorter treatment time until the age of 6 months at the beginning of therapy. Parents reported satisfaction and child compliance. Almost all parents were convinced that treatment was useful and would repeat it again.

350 nm and 550 nm thick InGaN/GaN bilayers were irradiated with different energies (from ∼82 to ∼38 MeV) of xenon (129Xe) ions and different fluences of 1.2 GeV lead (208Pb) ions, respectively.

Purpose Glioma patients, especially recurrent glioma, suffer from a poor prognosis. While advances to classify glioma on a molecular level improved prognostication at initial diagnosis, markers to prognosticate survival in the recurrent situation are still needed. As 18 kDa translocator protein (TSPO) was previously reported to be associated with aggressive histopathological glioma features, we correlated the TSPO positron emission tomography (PET) signal in a large cohort of recurrent glioma patients with their clinical outcome. Methods In patients with TSPO PET at glioma recurrence, TSPO PET parameters (e.g. SUVmax) as well as other imaging features (e.g. MRI volume, [18F]FET PET parameters when available) were evaluated together with patient characteristics (age, sex, Karnofsky-Performance score) and neuropathological features (e.g. WHO grade, IDH-mutation status). Uni- and multivariate Cox regression and Kaplan-Meier survival analyses were performed to identify prognostic factors for post-recurrence survival (PRS) and time to treatment failure (TTF). Results 88 consecutive patients were evaluated. TSPO tracer uptake correlated with tumor grade at recurrence (p IDH-wildtype versus IDH-mutant tumors. Within the subgroup of IDH-mutant glioma (n = 46), patients with low SUVmax (median split, ≤ 1.60) had a significantly longer PRS (median 41.6 vs. 25.3 months, p = 0.031) and TTF (32.2 vs 8.7 months, p = 0.001). Also among IDH-wildtype tumors (n = 42), patients with low SUVmax (≤ 1.89) had a significantly longer PRS (median not reached vs 8.2 months, p = 0.002). SUVmax remained an independent prognostic factor for PRS in the multivariate analysis including CNS WHO grade, IDH status and age. Tumor volume defined by [18F]FET PET or contrast-enhanced MRI correlated weakly with TSPO tracer uptake. Treatment regimen did not differ among the median split subgroups. Conclusion Our data suggest that TSPO PET can help to prognosticate recurrent glioma patients even among homogeneous molecular subgroups and may therefore serve as valuable non-invasive biomarker for individualized patient management.

The effects of 129Xe swift-heavy ion (SHI) irradiation on the optical and structural properties of InGaN/GaN multiple quantum wells (MQWs) are studied using non-destructive optical spectroscopy techniques. Through excitation wavelength-dependent μ-Raman spectroscopy, it is possible to identify the damage profile and to notice the surface region (around the first 40 nm) as the most affected one. Independent Rutherford backscattering spectrometry in channelling mode experiments corroborate this. By using resonant excitation with InGaN electronic states, it is possible to observe an increase of the A1(LO)InGaN phonon intensity for higher SHI energies. This is attributed to intermixing at the MQWs’ interfaces for electronic energy losses above 20 keV nm−1. Photoluminescence studies reveal an intense yellow emission band (YB) with two distinct contributions: excitonic (InGaN) and deep-level defects (GaN). After irradiation, strong luminescence intensity quenching and a change in its excitation mechanisms occur. The YB is no longer excited with energy above the GaN bandgap, but instead through an excitation band (at about 2.75 eV) attributed to gallium vacancies introduced in the GaN barriers. The strong quenching of the luminescence reveals that SHI irradiation introduces detrimental defects in the structure, which may compromise its use (without additional post-implantation treatments) for obtaining more efficient green light emitters based on InGaN/GaN MQWs.

Corticobasal syndrome (CBS) is a rare neurodegenerative condition characterized by four-repeat tau aggregation in the cortical and subcortical brain regions and accompanied by severe atrophy. The aim of this study was to evaluate partial volume effect correction (PVEC) in patients with CBS compared to a control cohort imaged with the 18-kDa translocator protein (TSPO) positron emission tomography (PET) tracer [

To compare flow-regulated (FR) and differential pressure (DP) valves for treatment of patients with idiopathic normal hydrocephalus (iNPH) focusing on overdrainage and neurological outcome. This is a retrospective study of patients with iNPH treated with FR and DP valves at a single institution between 2008 and 2018. The neurological status was evaluated retrospectively with the Kiefer scale at baseline, after shunt placement and at the 6-month follow-up. Groups were compared using inverse probability of treatment weighting based on propensity scores. The study cohort consisted of 38 patients treated with FR valves and 49 with DP valves. The mean patient age was 72.0 ± 7.6 years. Based on the Kiefer scale score, neurological improvement at the 6-month follow-up was recorded in 79.6% in the DP group and 89.5% in the FR group (p = 0.252). The overdrainage rates were higher among DP valves (10.2%) than among FR valves (2.6%, adjusted p = 0.002). Valve malfunction occurred in 2.0% in the DP group and 5.3% in the FR group (adjusted p = 0.667). The current study demonstrates a comparable neurological improvement between DP and FR valves, with potentially lower overdrainage rates among FR valves. Long-term studies will be necessary to draw a definite conclusion on FR valves for treatment of iNPH patients.

The elastic properties of the cubic (c-) phase GaN confined in a nanoscale one-dimensional (1D) v-grooved Si(001) substrate are investigated. Along a ∼900 nm-wide v-groove formed with two facing Si(111)-type facets, sub-micrometer-wide c-GaN is achieved by the hexagonal- to c-phase (h–c) transition from the h-GaN which plays the role of an interlayer in its epitaxy on Si. The resulting nonplanar stack of c-GaN/h-GaN on Si has complicated stress distribution. This work focuses on the elastic properties the c-GaN, which are critically affected by its low dimensionality, and presents experimental evidence for it with an analytical stress modeling. A reciprocal lattice map reveals that the c-GaN in each groove consists of several micrometer-long single crystals which are microscopically tilted from each other in their serial coalescence, as its unit structures. The corresponding micrometer-scale lateral correlation length, dc, results from the h–c transition that is interrupted by the groove imperfections gen...

Overdrainage and frequent reprogramming are common issues with programmable valves after ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Flow-regulated valves may address these limitations, but data on their efficacy are sparse. We present our single-center experience with flow-regulated valves focusing on overdrainage and efficiency.Thirty-two patients with iNPH treated with the Integra® NPH Low Flow Valve were prospectively enrolled. Clinical evaluation was performed at baseline, postoperatively as well as 3 and 6 months after surgery. The outcome was assessed by employing the iNPH grading scale and the Mini Mental Status Examination (MMSE). Overdrainage was assessed clinically and radiologically by computed tomography.The mean patient age was 71 years. All patients presented with gait disturbance, 29 had cognitive impairment and 25 had urinary incontinence. The mean duration of symptoms was 22.9 months. At 3-month follow-up, 25/31 patients (80.6%) improved on the total iNPH score by at least 5 points (p 0.001). The mean MMSE score increased from 24.5 to 26.1 points (p = 0.013). After 6 months, the improvement rates of the iNPH (82.1%) and the MMSE scores (26.8 points) were stable. The rate of clinically significant overdrainage was 3.2%. One patient presented with subdural hygromas that necessitated evacuation. In the remaining patients, clinical and radiological signs of overdrainage were absent.The use of the Integra® NPH Low Flow Valve leads to a good neurological outcome and has low overdrainage rates without the need for reprogramming. These results are encouraging and justify further investigation of this valve.

InSe, a newly rediscovered two-dimensional (2D) semiconductor, possesses superior electrical and optical properties as a direct-band-gap semiconductor with high mobility from bulk to atomically thin layers and is drastically different from transition-metal dichalcogenides, in which the direct band gap only exists at the single-layer limit. However, absorption in InSe is mostly dominated by an out-of-plane dipole contribution, which results in the limited absorption of normally incident light that can only excite the in-plane dipole at resonance. To address this challenge, we have explored a unique geometric ridge state of the 2D flake without compromising the sample quality. We observed the enhanced absorption at the ridge over a broad range of excitation frequencies from photocurrent and photoluminescence (PL) measurements. In addition, we have discovered new PL peaks at low temperatures due to defect states on the ridge, which can be as much as ∼60 times stronger than the intrinsic PL peak of InSe. Interestingly, the PL of the defects is highly tunable through an external electrical field, which can be attributed to the Stark effect of the localized defects. InSe ridges thus provide new avenues for manipulating light-matter interactions and defect engineering that are vitally crucial for novel optoelectronic devices based on 2D semiconductors.

Providing concise proof of child abuse relies heavily on clinical findings, such as certain patterns of injury or otherwise not plausibly explainable trauma. Subdural hemorrhaging has been identified as a common occurrence in abused children whereas epidural hemorrhaging is related to accidents. In order to explore this correlation, we retrospectively analyzed clinical data of children under 19 years of age diagnosed with either injury. Reviewing 56 cases of epidural and 38 cases of subdural bleeding, it was shown that subdural bleeding is more common in young children and extremely often a result of suspected abuse in children under 2 years of age. Epidural hemorrhaging however never was found in the context of suspected abuse, was unrelated to other injuries typical for abuse, and did not see a statistically significant increase in any age group. In conformity with currently theorized mechanisms of injury for both types of bleeding, we found that subdural hemorrhaging in young children is closely associated with abuse whereas epidural bleeding is not.

Although the risk of aneurysm remnants after microsurgical clipping is generally low, complete aneurysm occlusion is not always guaranteed. We performed a morphometric analysis of intracranial aneurysms to identify predictors for aneurysm remnants and to propose a novel risk score.This is a retrospective, single-center analysis of consecutive patients with ruptured and unruptured aneurysms who underwent microsurgical clipping and postoperative digital subtraction angiography between 2010 and 2018. Based on preoperative rotational angiography, distinct morphologic aneurysm characteristics were determined and correlated with postoperative angiographic results. Factors predictive in the univariate and multivariate analyses were determined to establish a risk score for postoperative remnants after aneurysm clipping.Among 140 patients with 166 clipped aneurysms, aneurysm remnants were present in 19.9%. In the multivariate analysis, ruptured aneurysm status (odds ratio [OR], 7.8; 95% confidence interval [CI], 1.7-36; P0.01) and increased aspect ratio (OR, 1.9; 95% CI, 1.0-4.0; P = 0.07) were associated with postoperative aneurysm remnants. Anterior communicating artery location (P = 0.02), internal carotid artery location (P = 0.06), increased aneurysm inclination angle (P0.01), and irregular aneurysm shape (P = 0.07) were further predictors for aneurysm remnants in the univariate analysis. These factors were weighted and included into a risk sum score for postoperative aneurysm remnants (range, 0-8 points), which performed with good accuracy (area under the curve = 0.807).After external validation of the proposed risk score, it could help identify cases requiring angiographic control after aneurysm surgery.

For the sustainable redevelopment of existing properties,it is important thatthe measures taken pay off economically as well. With the energy-scoring method presented in this paper, portfolios can be classified according to their energy-saving potential. Besides the various factors affecting the reduction of primary energy demand, the 3-tier model analyzes and correlates the economic efficiency. The result is an objective ranking of each object, from which property owners can deduce where they should ideally invest in order to optimize the energy efficiency of their building stock sustainably.

An atomic-scale phase transition in heterophase epitaxy (HPE) of GaN on a 900 nm-wide v-grooved Si(001) substrate is reported. Two different incorporation mechanisms of adatoms sequentially occur for the hexagonal (h-) to cubic (c-) phase transition: orientation- and phase-dependent incorporation (ODI and PDI). Epitaxy begins with ODI that results in preferential growth of h-GaN individually aligned to opposing Si(111) facets inside a v-groove but incurs a structural instability by crystallographic mismatch at the groove bottom. This instability is relieved by an abrupt transition to c-phase, initiating from single or multiple atomic sites uniquely arranged atop the mismatch along the groove. Epitaxy proceeds with PDI that allows μm-scale c-GaN extended from these sites while suppressing growth of h-GaN. An important condition for HPE and the stability of c-GaN in further growth is derived from equilibrium crystal shape.

We present a simple and robust method to acquire quantitative maps of compositional fluctuations in nanostructures from low magnification high-angle annular dark field (HAADF) micrographs calibrated by energy-dispersive X-ray (EDX) spectroscopy in scanning transmission electron microscopy (STEM) mode. We show that a nonuniform background in HAADF-STEM micrographs can be eliminated, to a first approximation, by use of a suitable analytic function. The uncertainty in probe position when collecting an EDX spectrum renders the calibration of HAADF-STEM micrographs indirect, and a statistical approach has been developed to determine the position with confidence. Our analysis procedure, presented in a flowchart to facilitate the successful implementation of the method by users, was applied to discontinuous InGaN/GaN quantum wells in order to obtain quantitative determinations of compositional fluctuations on the nanoscale.

In this paper, we have investigated the high temperature characteristics of monolithically integrated LED and MOS-channel HEMT in GaN. The monolithically integrated LED/MOSC-HEMT was implemented by using a selective epi removal approach. The temperature dependence of optical and electrical characteristics of the integrated LED is found to be comparable to that of discrete GaN based LEDs. On-resistance of the MOSC-HEMT shows gradual increase with temperature (~1.6× increase from 25 °C to 225 °C) whereas LED LOP shows rapid decrease with temperature (~6× decrease from 25 °C to 225 °C). Light output of the integrated LED is modulated by the MOSC-HEMT gate bias up to 225 °C.

We report that using a high/low p-type junction anode structure results in improved hole injection over a uniformly-doped p-anode layer in GaN pin junction diodes. Quasi-vertical diodes with a 20 nm thick, magnesium concentration of 2 × 1020 cm−3 layer on top of a 480 nm thick layer with a magnesium concentration of 1018 cm−3 show greatly increased forward current density – >100× higher – than those with a 500 nm thick uniformly 3 × 1019 cm−3 Mg-doped p-layer. Forward knee voltage and ideality factor are reduced by a factor of more than two, and reverse leakage current density is also reduced. Additionally, the specific differential series resistance is reduced significantly. With photoluminescence measurements, we found that these improvements are largely due to improved p-GaN material quality of the high/low junction sample with lower average Mg concentration.

The initial stages of the nucleation of cubic (c-) GaN in heterophase epitaxy on a Si v-groove are investigated. Growth of GaN on a nanoscale {111}-faceted v-groove fabricated into a Si(001) substrate proceeds in the hexagonal (h-) phase that induces a secondary v-groove replicating the substrate topography with two opposing {0001} facets. The secondary v-groove is then orientationally mismatched at the junction of the h-GaN facets (h -h junction) resulting in structural instability. This instability is relieved either by the formation of voids that reduce the actual junction area or by the transition to c-phase (h-c transition) suppressing further extension of the h-h junction. The distribution of voids that is locally affected by the island growth mode of h-GaN on Si(111) and the imperfection in the groove geometry impacts the initial stage of heterophase epitaxy. Primarily, The h-c transition is observed as a non-local phenomenon; it occurs homogeneously and simultaneously along the bottom of the entire secondary groove and forms a one-dimensional (1D) seed layer except for some interruptions where the h-h junction is defected by gaps or incomplete voids. Between these interruptions, epitaxy retains a single crystal but results in a series of c-GaN nanodots on the seed layer with large fluctuation in size and spacing. The adatom incorporation observed in this heterophase epitaxy is a 1D analog to the wetting of a substrate followed by the self-assembly in conventional quantum dot epitaxy. The surface morphology of the c-GaN nanodots is governed by the faceting mostly composed of (001)- and (11n)-orientations and the roughening between these facets that ultimately affect the morphology of the final top surface of the c-III-N. The interruptions interfere with the homogeneity of the h-c transition and can cause antiphase defects and mosaicity. Based on experimental results, a solution to improve these issues is proposed.

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.

We studied the optical properties of metalorganic chemical vapour deposited (MOCVD) InGaN/GaN multiple quantum wells (MQW) subjected to nitrogen (N) implantation and post-growth annealing treatments. The optical characterization was carried out by means of temperature and excitation density-dependent steady state photoluminescence (PL) spectroscopy, supplemented by room temperatura PL excitation (PLE) and PL lifetime (PLL) measurements. The as-grown and as-implanted samples were found to exhibit a single green emission band attributed to localized excitons in the QW, although the N implantation leads to a strong reduction of the PL intensity. The green band was found to be surprisingly stable on annealing up to 14006C. A broad blue band dominates the low temperature PL after termal annealing in both samples. This band is more intense for the implanted sample, suggesting that defects generated by N implantation, likely related to the diffusion/segregation of indium (In), have been optically activated by the thermal treatment, The authors acknowledge FCT for the final funding from PEst-C/CTM/LA0025/2013-14, PTDC/CTM-NAN/2156/2012, PTDC/FIS-NAN/0973/2012 and RECI/FIS-NAN/0183/ 2012 (FCOMP-01-0124-FEDER-027494) projects. J. Rodrigues thanks FCT for her PhD grant, SFRH/BD/76300/2011. ARC acknowledges financial support under the ‘Juan de la Cierva’ program (MECO, Spain) through grant JCI-2012-14509.

We model and optimize various light emitting diode structures under bias voltage to maximize emission efficiency with particular respect to piezoelectric polarization. We compare polar and non-polar structures, namely, wurtzite c-plane, a-plane, (11–22) semi-polar, and (001) cubic crystal orientations in self-consistent Schrodinger-Poisson and drift-diffusion models. We consider both structures strained to a GaN pn-junction and strain-reduced systems based on GaInN templates. In light of numerous experimental findings of the actual electric field strength, we find it necessary to reduce the piezoelectric coefficients over those commonly cited. A weaker variation with composition or wavelength is the consequence. For the non-polar and cubic systems, we find a 22% increase of the electron-hole overlap and an 18% increase for the c-plane strain-reduced system at an InN fraction of x = 0.30 when compared to standard c-plane structures. For the green and longer wavelength range, we find that strain-reduced and...

Low-defect density non-polar a-plane Ga1-yInyN layers on r-plane sapphire substrates are reported by implementing self-assembling nanopatterning in metalorganic vapor phase epitaxy. Nanopillar capping and void formation in regrowth lead to a 90% defect reduction. An ex-situ Ni layer transforms into a nanoisland etch mask to pattern GaN templates. a-Plane GaN and Ga1-yInyN layers with an InN content in the range of y = 0.04–0.11 are then regrown. Both exhibit a low density of basal-plane stacking faults of (4.6 ± 1.3) × 104 cm−1 by transmission electron microscopy analysis. Growth parameters and the template pattern are discussed by help of an X-ray rocking curve analysis. We find pattern the fill factor and V/III ratio to dominate the defect reduction. Resulting layers should enable efficient long-wavelength light-emitting and solar cell devices.

The incorporation of In on the non-polar, piezoelectric-free (001) facet of cubic (c-) GaN epitaxially grown over a Si(001) substrate by metal-organic vapor phase epitaxy is reported. Relying on a hexagonal (h-) to c-phase transformation during epitaxy on an 800 nm-wide, Si(111)-faceted v-groove patterned into the substrate, the GaN epilayer at cross sectional view retains a triangular c-phase inside a chevron-shaped h-phase that results in a top surface bounded by a (001) facet parallel to Si(001) at the center and ( 11¯01) facets at both edges. A stack of five, ∼3 nm-thick, InxGa1−xN/GaN quantum wells (QWs) was deposited on the double-phased top surface. The c-phase region up to the QWs keeps extremely small misfit (∼0.002) to the fully relaxed h-GaN underneath it and is in tensile stress implying undefected by the h-c phase interface. The In incorporation on a strained non-polar (001) of c-GaN is comparable with that on totally relaxed semi-polar ( 11¯01) of h-GaN without noticeable adatom migration ac...

Ion-induced damage and intermixing was evaluated in InGaN/GaN multi-quantum wells (MQWs) using 35 keV N(+) implantation at room temperature. In situ ion channeling measurements show that damage builds up with a similar trend for In and Ga atoms, with a high threshold for amorphization. The extended defects induced during the implantation, basal and prismatic stacking faults, are uniformly distributed across the quantum well structure. Despite the extremely high fluences used (up to 4 × 10(16) cm(-2)), the InGaN MQWs exhibit a high stability against ion beam mixing.

By some accounts group-III nitride may be the widest disseminated man-made compound semiconductors. Yet, what is it that makes it so successful? Maybe the wurtzite structure which allows for piezoelectric polarization? We know about the Stokes shift it induces and its associated troubles. So we rush to reduce polarization in non-polar growth. But how about the cubic form of GaN. Shouldn't that be free of polarization? Would it be the better light emitter even? To find out we prepare GaN and GaInN/GaN heterostructures in cubic lattice form. Yes, that has been done before but in MBE. No, we use MOVPE, the method responsible for all the bright emitters in the nitrides. By virtue of some patterning we achieve cubic growth on the more common form of Si, the (001) orientation, which further allows for conceptional integration with the semiconductor of industry choice. We discuss details of the epitaxial growth and progress in characterization results including first green LEDs.

Achieving p-type conduction in GaN has poised the material a power semiconductor on all fronts. Record conversion efficiencies and power densities in LEDs render it a platform of GW installation base. After commercial success as a blue light emitter, the emphasis now rests on the expansion of its capacity as a full spectrum direct emitter --- and absorber. Green and amber LEDs will allow full control of lighting quality and specificity in photochemistry. In early results we find evidence of temperature performance crucially superior to those of the incumbent. Next, we explore the same GaInN/GaN quantum wells as a concentration solar cell converter. While definitely limited to the short wavelength range so far, we find respectably high spectral conversion efficiencies and outstanding temperature stability. Such performance, however, is just early indication of what else lies ahead in terms of power electronics in the form of lateral and vertical transistor. In early results we monolithically integrate LED and transistor.