Ilkay Demir

Ilkay Demir
Sivas Cumhuriyet University · Department of Nanotechnology Engineering

PhD

About

38
Publications
5,152
Reads
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140
Citations
Additional affiliations
August 2020 - present
Sivas Cumhuriyet University
Position
  • Professor (Associate)
March 2018 - August 2020
Sivas Cumhuriyet University
Position
  • Professor (Assistant)
December 2014 - December 2015
Northwestern University
Position
  • Researcher

Publications

Publications (38)
Article
We report the growth of high quality InGaAs/InAlAs quantum cascade laser (QCL) structure which composed of superlattices (SLs) and the effects of interruption time between each layer of the SL structure. Inserting an interruption delay during the growth dramatically effects the quality of the SL as indicated by crystallinity, interface sharpness an...
Article
In this study we report the V/III ratio effects on growth, structural, optical and doping characteristics of low growth rate (∼1 Å/s) heteroepitaxial Metal Organic Chemical Vapor Deposition (MOCVD) grown InxAl1-xAs layers, a part of Quantum Cascade Laser (QCL) structures, on InP substrate. Especially photoluminescence (PL) properties of InAlAs-InP...
Article
We report on the close oxygen coupled low-pressure chemical vapor deposition (COC-LPCVD) hetero-epitaxial growth of atomically smooth (−201) oriented β−Ga2O3 on c-plane sapphire. Utilizing a dedicated line within the main tube, O2 could be delivered to the substrate surface which enables effective control of growth regime. Under optimized condition...
Article
This paper reports the temperature effects on the optical properties of metalorganic vapour-phase epitaxy (MOCVD) grown c-axis oriented AlN epilayer thin film studied by in-situ high-temperature spectroscopic ellipsometry. The crystal structure and the quality of the grown AlN epilayer film are analyzed using X-ray Diffraction and rocking curve tec...
Article
AIN is used as a template layer for deep UV (DUV) emitter and detector applications, because of its wide bandgap and high thermal conductivity. In this study, trimethylgallium (TMGa) source is used as surfactant to improve crystal quality and decrease dislocation density (DD) of AlN layers grown on sapphire (Al2O3) substrate surfaces by Metal Organ...
Article
AlN films have been deposited on c-plane sapphire substrates by metalorganic-vapor-phase-epitaxy (MOVPE). The changes in the film structure have been investigated by applying different annealing processes which are ex-situ rapid thermal annealing (RTA) and in-situ process after the nucleation-layer (NL). The AlN nucleation-layer grown on sapphire h...
Article
In this study, we report different SiH4 flow condition effects on crystal, surface, optical, and electrical characteristics of heteroepitaxial Metal-Organic Vapor Phase Epitaxy (MOVPE) grown AlN layers on sapphire substrates. Adjustment of growth kinetics is very important to control the doping. Therefore, pulsed atomic layer epitaxy (PALE) was use...
Article
Achieving high threshold current density and high optical confinement are big challenges in the realization of high-performance aluminum gallium nitride (AlGaN)-based deep-ultraviolet (DUV) laser diode (LD). In this work, compositional Al-grading of AlGaN layers is used to increase the optical confinement factor (OCF), carrier injection efficiency,...
Article
Optical and structural properties in high-x InxGa1-xAs (x > 0.65) samples with varying indium concentration grown on InP (1 0 0) substrate are reported. By increasing the indium fraction, it was found by the high-resolution X-ray diffraction (HR-XRD) study that the dislocation density in the InxGa1-xAs epitaxial layer significantly increased, and t...
Article
InGaN-based quantum wells (QWs) have higher threading dislocation density (TDD) in InGaN Light-emitting diode (LED). Despite of higher TDD, variation of Indium (In) molar fraction in the QW generate localized excitons with higher Indium composition, thus preventing bound carriers from non-radiative recombination. In this work, the sensitivity of th...
Article
The free buffer InGaAs/InP structure has been elaborated by Metal Organic Vapor Phase Epitaxy (MOVPE). High indium content is chosen to reduce the bandgap energy of the ternary material with direct bandgap to be promoted for Infrared optoelectronic devices. In this work, the temperature dependent photoluminescence (TDPL) analysis of In-rich In x Ga...
Article
Full-text available
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), atomi...
Article
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 120 W power value. Then 250 nm ZnO was grown on these thin films. Microstructural analyses of the thin films were made by scanning electron micr...
Article
In the present study, the PALE-AlN (pulsed atomic layer epitaxy) epilayers were grown on the Si (111) substrates at different growth temperatures by metal organic vapor phase epitaxy (MOVPE) technique. The oxygen (O) and silicon (Si) concentrations of grown PALE-AlN epilayers and interface between epilayer and substrate were investigated by seconda...
Article
In-rich In x Ga 1−x As epitaxial layers were grown on InP (1 0 0) substrates by a metalorganic vapor phase epitaxy (MOVPE) technique. The effect of Indium (In) composition on the crystalline quality and optical properties are investigated. High resolution X-ray diffraction (HR-XRD) measurement and Raman scattering spectrum are used to evaluate the...
Article
We investigate the influences of GaAs buffer layer (bl) growth parameters such as temperature and thickness on the structural, morphological, crystalline and optical quality of metal organic vapor phase epitaxy (MOVPE) grown heterostructures of GaAs on Ge. It has been found that the optimal bl conditions significantly decrease the effects of anti-p...
Conference Paper
In this work, the effect of introducing a photonic crystal network of silicon nitride (SiN) micro-domes on the backside of silver coated gallium nitride (GaN) based light emitting diodes (LEDs) was studied. First, sapphire side of the top emitting LEDs, which is the bottom surface of the LEDs, is coated with silver (Ag). Light emitted towards the s...
Article
We report a new growth approach pulsed co-doping growth of AlxGa1−xN (x > 0.5) epilayers on AlN/Al2O3 templates by metal organic vapor phase epitaxy (MOVPE). Using this approach SiH4 (silane) and TMIn (trimethylindium) supplied to the growth chamber alternately and pulsed during the growth of AlGaN epilayers. Structural and morphological quality of...
Article
We report the effects of AsH3 (arsine) on morphological, structural, optical and crystalline quality of MOVPE (metal organic vapor phase epitaxy) grown GaAs/Ge heterostructures. AsH3 pre-flow supplied on Ge substrate to have As atoms as a first atomic layer on the surface of Ge substrate. Additionally, the V/III ratio effects of LT-GaAs buffer laye...
Article
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 µm thick AlN layer of high crystalline quality. X-ray diffraction characterization showed a rocking curve with a full width at half maximum of...
Article
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 carr...
Article
We present growth and characterization studies of highly n-doped InGaAs epilayers on InP substrate by metal organic vapor phase epitaxy to use as an n-contact layer in quantum cascade laser applications. We have introduced quasi two-dimensional electrons between 10 s pulsed growth n-doped InGaAs epilayers to improve both carrier concentration and m...
Article
The aim of the study is to understand the effects of two stages of HT-GaN growth with different V/III ratios on optical, chemical and structural characteristics of the HT-GaN layer. In addition, the effects of two-stage growth on the transport properties has been presented through fabricated Schottky diodes. As the V/III ratio in the 1st stage grow...
Article
We report pulsed atomic layer epitaxy (PALE) growth of very high crystalline quality, thick (~2 µm) and crack-free AlN material on c-plane sapphire substrates via a sandwich method using metal organic chemical vapor deposition (MOCVD). This sandwich method involves the introduction of a relatively low temperature (1050 °C) 1500 nm thick AlN layer b...
Article
Full-text available
InxGa1-xAs tabakaları katkısız InP (100) alttaş üzerine Aixtron 200-4 RF/S yatay Metal Organik Kimyasal Buhar Depolama (MOCVD) sistemi ile büyütülmüştür. Bütün epikatmanlar farklı indiyum konsantrasyonlarında büyütülmüştür. Katmanların kalınlıkları Taramalı Elektron Mikroskobu (SEM) ile ölçülmüştür. İndiyum konsantrasyonları Yüksek Çözünürlüklü X-ı...
Article
AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5–10mm thick AlN grown by LEO is comparable to that of much thinner layers (2 mm) grown by cantilever...
Article
AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5–10mm thick AlN grown by LEO is comparable to that of much thinner layers (2 mm) grown by cantilever...
Article
Full-text available
In this study, we report the growth studies of InGaAs/InAlAs superlattices (SLs) with thin layer thicknesses which will be used for quantum cascade laser (QCL) structures, grown by Metal Organic Chemical Vapor Deposition (MOCVD) technique. We utilize high resolution X-ray diffraction (HRXRD) to determine the single layer thickness and period thickn...
Presentation
Full-text available
InGaAs/InAlAs superlattice (SL) structures are crucial for mid-far infrared semiconductor lasers and photodetectors for trace gas sensing, free-space optical communications etc. Especially quantum cascade laser (QCL) structures require very high crystallinity and interface quality. These type of structures generally are grown by Molecular Beam Epit...
Presentation
Full-text available
Indium Gallium Arsenide (InxGa1-xAs) compound semiconductors on indium phosphide (InP) substrate have a lot of applications due to range of band gap (0.86-3.54µm) available through the composition range and its superior properties. They have been extensively used for electronic and optoelectronic devices. In terms of growth conditions, AsH3 flow wh...
Article
Full-text available
We have calculated the binding energy for the ground state of a heavy-hole exciton in GaAs/Ga0.7Al0.3As cylindrical quantum well wires (CQWWs) under the action of a hydrostatic pressure, temperature and magnetic field. The calculations are made using variational methods and the effective mass approximation for a finite confinement potential. The hy...
Thesis
In this work, we have investigated epitaxial single crystal GaN thin films grown on sapphire substrate by Rigaku SmartLab x-ray diffraction facility that is founded in Nanotechnology Laboratory in our university . In addition we have determined the density of dislocations, vertical and lateral coherence lengths, tilt and twist angles of the sample...

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Projects

Projects (3)
Project
Using clean AlGaN/ AlN/GaN based UV Technologies for Medical and Agricultural Applications
Project
In this project, it is aimed to grow epitaxial AlN crystal with MOCVD, to dope this AlN crystal, to characterize, to produce the device and to investigate of diode characteristics for the high power-frequency applications.
Project
In this project, high-quality AlN layer which is used as a template in the production of new generation semiconductor ultraviolet light producing sources and detectors is aimed to be grown in high crystal quality by MOCVD using pulse atomic layer epitaxial technique on a nonpatterned silicon substrate.