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InxGa1−xAs epitaxial layers with different AsH3 flows have been grown on InP substrate with the MOVPE system. It has been found that AsH3 flow variation affects the In concentration of InGaAs/InP structure because the increment of AsH3 flow increases the In concentration due to the weak bond between In and As. The variation of AsH3 flow during the growth process has affected crystal quality and optical properties of InGaAs epilayer. The optical properties of the structure have been determined by spectroscopic ellipsometry and spectrophotometer. The variation of In concentration has changed the refractive index value of the structure. The thickness of the samples and refractive index values have been obtained by spectroscopic ellipsometry. The obtained findings show that the reflection has been improved with high AsH3 flow resulting from surface quality improvement. In addition, it has been observed that the energy band gap has been decreased as a function of the increment of AsH3 flow because the structure band gap approaches the InAs structure at the high In concentration., This work is supported by the Scientific Research Project Fund of Sivas Cumhuriyet University under the project number [M-2021–821].

AlN samples have been grown on sapphire substrate using nucleation layers (NLs) having different growth temperatures. The growth temperature of the NL has been varied over a wide range of temperatures highlight the effects on the quality of the AlN epilayer. The AlN samples have been characterized by high-resolution X-ray diffraction (HRXRD), atomic force microscope (AFM), Raman scattering spectrometer, and spectrophotometer. The obtained results demonstrate the temperature of NL has a direct effect on the quality of the AlN sample and occurs major differences in the quality of structure, surface morphology, and amount of strain in the AlN epilayers. Based on HRXRD measurement results, when the growth temperature of AlN NL is raised to 1075 degrees C, the crystal quality has improved owing to both the density of AlN nucleation islands reduction and the grain size outgrow. However, continuing to increase the growth temperature of the AlN NL layer begins to degrade the quality. In addition, the findings obtained from the Raman measurement demonstrates that the tensile stress can be control through NL growth temperature. Therefore, as can be seen from the characterization results, the growth temperature of AlN NL is important to obtain an AlN sample with high quality.

This study was conducted in Sivas Cumhuriyet University R & D Center (CUTAM), Sivas Cumhuriyet University Nanophotonic Application and Research Center., In this study, Al2O3 thin films of different thicknesses (50 nm, 100 nm, 150 nm, 200 nm, and 250 nm) were, first, grown using RF magnetron sputtering technique on glass substrate at 30 °C temperature, with 120Wpower value. Then 250 nm ZnO was grown on these thin films. Microstructural analyses of the thin films were made by scanning electron microscope (SEM). It was observed that the particle size changed with increasing thickness of Al2O3 thin films. ZnO layer was grown onto alumina grown tubes with an approximate thickness of 250 nm. The grain morphology of ZnO was similar to alumina, about 25–30 nm grain size. Energy-dispersive X-ray analysis (EDX) detector was used to determine the chemical composition of the samples. These results have indicated that ZnO thin films are successfully formed on alumina tubes. Crystal structure analyses of all samples were examined using the X-ray diffraction (XRD) technique. In addition, the optical properties of the samples were examined with ultraviolet-visible-near infrared spectrometer (UV-VIS-NIR). This work provides valuable references for the application of Al2O3 as insulating buffer layers., This research was supported by Scientific Research Project Fund of Sivas Cumhuriyet University under the project number RGD-32.

Present study aimed to examine the relative role of time spent on the internet, parents’ educational background and parental mobile phone and computer monitoring behaviors on problematic internet use among adolescents. Participants of the study were 250 high school students from İstanbul aged between 14 and 18. Problematic Internet Usage scale, Parental Monitoring Scale and Demografic Information Form were used to collect data. Results of the hierarchical regression analysis revealed that time spent on the internet, fathers’ education and parental computer monitoring together accounted for the 16% of the variance in problematic internat use among adolescents. While mothers’ educational background and parental mobile phone monitoring had no significant contribution in the model, time spent on the internet and fathers’ education were found to be stronger predictors of problematic internet use than parental computer monitoring.

WOS: 000450320600014, We report on the fabrication of high brightness AlGaN-based ultraviolet light emitting diodes (UV-LED) on patterned silicon. Using the lateral epitaxial overgrowth approach, we demonstrate the growth of a 6 mu m thick AIN layer of high crystalline quality. X-ray diffraction characterization showed a rocking curve with a full width at half maximum of 553 and 768 '' for the (00.2) and (10.2) planes, respectively. The low dislocation density of the AIN template enabled the growth of bright AlGaN/GaN quantum wells emitting at 336 nm. By appropriate flip-chip bonding and silicon substrate removal processing steps, the patterned AIN surface was exposed and efficient bottom-emission UV-LEDs were realized. Improvement of the AIN quality and the structure design allowed the optical output power to reach the milliwatt range under pulsed current, exceeding the previously reported maximum efficiency. Further investigations of the optical power at different pulsed currents and duty cycles show that thermal management in this device structure is still challenging, especially in continuous wave mode operation. The strategy presented here is of interest, since AIN crystalline quality improvement and optimization of the light extraction are the main issues inhibiting efficient UV emitter on silicon fabrication.

WOS: 000463693300002, This paper presents high performance, GaN/InGaN-based light emitting diodes (LEDs) in three different device configurations, namely Top Emitting (TE) LED, conventional Flip Chip (FC) and Distributed Contact (DC) FC. Series resistances as low as 1.1 Omega have been obtained from FC device configurations with a back reflecting ohmic contact of Ni/Au/RTA/Ni/Ag metal stack. A small shift has been observed between electroluminescence (EL) emissions of TE LED and the FC LEDs. In addition, FWHM value of the EL emission of DCFC LED has shown the minimum value of 160 meV (26.9 nm). Furthermore, DCFC LED configuration has shown the highest quantum efficiency and power output, with 330 mW at 500 mA current injection, compared to that of traditional wire bonded TE LEDs and the conventional FC LEDs., Scientific and Technical Research Council of Turkey, (TUBITAK) [113G042, 115E109], We are grateful to H. Morkoc, U Ozgur, V. Avrutin of Virginia Commonwealth University for many fruitful discussions. This work is supported by Scientific and Technical Research Council of Turkey, (TUBITAK Grant no: 113G042 and 115E109).

In this work, MOVPE (Metalorganic Vapor PhaseEpitaxy) growth and characterization studies of high Al content AlGaN epilayersare reported. We utilize high resolutionX-ray diffraction (HRXRD) and atomic force microscope (AFM) techniques toanalyze the crystalline quality andsurface morphology of AlGaN epilayers. The role of the growth temperature ofAlGaN epilayers on the structural quality and the surface morphology wasinvestigated. Growth and measurement results show that single phase AlGaNepilayers were grown on AlN/Al2O3 template. It isconcluded that the increasing growth temperature increases the Al content ofAlGaN epilayers which enable to control the alloy concentration of AlGaN.Furthermore, the increasing Al content in AlGaN epilayers leads to the smoothsurface which indicates that the decreasing number of dislocation density., Bu çalışmada, yüksekAl içerikli AlGaN epi-tabakaların MOVPE (Metalorganik Buhar Fazı Epitaksi)büyütmesi ve karakterizasyon çalışmaları rapor edilmiştir. AlGaNepi-tabakaların kristal kalitesi ve yüzey morfolojisi analizi için yüksekçözünürlüklü X-ışını kırınımı (HRXRD) ve atomik kuvvet mikroskobu tekniklerikullanılmıştır. Büyütme sıcaklığının AlGaN epi-tabakalarının yapısal kalitesive yüzey morfolojisi üzerindeki rolü incelenmiştir. Büyütme ve ölçüm sonuçlarıAlN/Al2O3 şablonu üzerine tek fazda AlGaN epi-tabakalarınbüyütüldüğünü göstermektedir. Artan büyütme sıcaklığının AlGaN'in Al içeriğiniarttırdığı ve bunun AlGaN alaşım konsantrasyonunu kontrol etmeye olanaksağladığı sonucuna varılmıştır. Ayrıca, AlGaN epi-tabakalarındaki Al içeriğininartışı pürüzsüz yüzeye yol açar ki budislokasyon yoğunluğunun azaldığını belirtir.

WOS: 000459827000007, We report the effect of total carrier gas flow of GaN during both GaN nucleation layer and high temperature GaN growth steps on structural, optical, electrical and morphological properties. The formation of dislocations in GaN layer and their effects were investigated in detail as a function of carrier gas flow. It has been found that the more carrier gas requires longer recovery time for transition from 3D (3 dimensional) to 2D growth and results in smaller edge-type dislocation density. The images obtained from the AFM measurements have shown terraces widths varying between 60-150 nm depending on the hydrogen flow rate., TUBITAK [113G103, 115E109]; Cumhuriyet University [M-699], The authors acknowledge the usage of Nanophotonics Research and Application Center at Cumhuriyet University (CUNAM) facilities. This work is supported by the TUBITAK under project nos. 113G103 and 115E109 and by Scientific Research Project Fund of Cumhuriyet University under the project number M-699. The authors thank Ms. A. Alev Kizilbulut from ERMAKSAN Optoelectronics for room temperature PL measurements.