Mustafa Ozturk

Metalorganic chemical vapor deposition growth and thermal stability of the AlInN/GaN high electron mobility transistor structure

The AlxIn1−xN barrier high electron mobility transistor (HEMT) structure has been optimized with varied barrier composition and thickness grown by metalorganic chemical vapor deposition. After optimization, a transistor structure comprising a 7 nm thick nearly lattice-matched Al0.83In0.17 N barrier exhibits a sheet electron density of 2.0 × 10 13 cm −2 with a high electron mobility of 1540 cm 2 V −1 s −1 .A n Al0.83In0.17N barrier HEMT device with 1 μm gate length provides a current density of 1.0 A mm −1 at VGS = 0 V and an extrinsic transconductance of 242 mS mm −1 , which are remarkably improved compared to that of a conventional Al0.3Ga0.7N barrier HEMT. To investigate the thermal stability of the HEMT epi-structures, post-growth annealing experiments up to 800 ◦ C have been applied to Al0.83In0.17N and Al0.3Ga0.7N barrier heterostructures. As expected, the electrical properties of an Al0.83In0.17N barrier HEMT structure showed less stability than that of an Al0.3Ga0.7N barrier HEMT to the thermal annealing. The structural properties of Al0.83In0.17N/GaN also showed more evidence for decomposition than that of the Al0.3Ga0.7N/GaN structure after 800 ◦ C post-annealing. (Some figures in this article are in colour only in the electronic version)

Mosaic Structure Characterization of the AlInN Layer Grown on Sapphire Substrate

The 150 nm thick, (0001) orientated wurtzite-phase Al1−xInxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 µm) template/(0001) sapphire substrate. The indium (x) concentration of the Al1−xInxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x), lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002) and asymmetric (10–15) reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations) of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles.

The Role of Serum Bilirubin Levels in Predicting Troponin Positivity in Non-ST-Segment Elevation Acute Coronary Syndrome.

Data are scant regarding serum bilirubin levels in non-ST-segment elevation acute coronary syndrome (NSTE-ACS). In this study, we evaluated the role of serum bilirubin levels in NSTE-ACS. We enrolled 782 patients who presented to the emergency department with acute chest pain. Patients were divided into 2 groups based on the troponin positivity. Patients with NSTE-ACS who had troponin positivity were included in group 1 (n = 382), and group 2 consisted of the control patients (n = 400). Direct bilirubin (DB) levels (group 1: 0.31 ± 0.37 mg/dL, group 2: 0.20 ± 0.25 mg/dL, P < .001) and total bilirubin (TB) levels (group 1: 0.78 ± 0.56 mg/dL, group 2: 0.62 ± 0.45 mg/dL, P < .001) were significantly higher in group 1. There was a significant and moderate correlation between serum bilirubin levels and admission troponin values (r = .34, P < .001 for TB and r = .42, P < .001 for DB). These results show that serum bilirubin levels were associated with troponin positivity in patients with NSTE-ACS.

The Comparison of Angiographic Scoring Systems With the Predictors of Atherosclerosis

Syntax score (SS) and Gensini score (GS) are used to determine the complexity and severity of coronary artery disease. Although there are some studies indicating the individual relationship of these scoring systems with the carotid intima–media thickness (cIMT) and epicardial fat tissue (EFT), there was no previous study that compared the SS and GS in that respect. We aimed to assess the relationship of SS and GS with predictors of atherosclerosis. We enrolled 522 patients. There were positive correlations between GS and SS tertiles with cIMT and EFT. According to multivariate linear regression analysis for GS, EFT (β: 0.035, t: 2.63, and P = .49) and cIMT (β: 0.339, t: 2.97, and P = .053) were not independently associated. For SS, EFT (β: 0.009, t: 6.5, and P = .006) and cIMT (β: 1.2, t: 10.1, and P = .001) were independently and significantly associated. We showed that the SS is significantly associated more with surrogate markers of atherosclerosis such as EFT and cIMT than the GS.

Calculation of Elastic Scattering Properties in Ultracold Fermi–Bose and Bose–Bose Rb–K Vapor

The calculation of the elastic scattering properties of mixtures composed of ultracold Rb–K atoms is reported and compared with experimental results in detail. The improved potentials for both the singlet and triplet molecular states of Rb–K are presented, and the scattering lengths a t and the effective range r e are calculated with numeric and semiclassical methods for Rb–K in the triplet and singlet state. In addition, the convergence of these scattering properties depending on a K 0 parameter is investigated using quantum defect theory. Other results of the evaporative cooling that include the cross section and the spin–charge cross section, the rate coefficient as a function of the energy and ultralow temperature are also presented in this study.