ahmet kürsat Bilgili - Profile on Academia.edu (original) (raw)

Papers by ahmet kürsat Bilgili

Journal of Science and Technology of Dumlupınar University, Jan 15, 2016

Ag/TiOz/n-loPl Au Schottky bariyerli diyotlarm akun-voltaj karakteristikleri 300-400 K sicaklik a... more Ag/TiOz/n-loPl Au Schottky bariyerli diyotlarm akun-voltaj karakteristikleri 300-400 K sicaklik arahgmda incelendi. Metal ile yarriletken arasina 120 A kahnhg mda TiO, film tabakasi o lusturuldu. Diyotun ileri beslem akim-voltaj (1-V) karakteristiklerinden termiyonik emisyon modeline gore, sifir beslem bariyer yiiksekligi ve idealite faktoru parametreleri hesaplandi. Parametre lerin sicakhga bagh olarak degi §tigi ve sicakhk artarken bariyer yuksekliginin arttig t ve idealite faktorunun azaldig i goruldu.

Applied Physics A, Jan 18, 2019

In this study, three InGaN/GaN light-emitting diode (LED) structures with five periods are invest... more In this study, three InGaN/GaN light-emitting diode (LED) structures with five periods are investigated grown by metal organic chemical vapor deposition (MOCVD) technique. During growth of these three samples, active layer growth temperatures are adjusted as 650, 667 and 700 °C. These structures are grown on sapphire (Al 2 O 3 ) wafer as InGaN/GaN multiquantum wells (MQWs) between n-GaN and p-AlGaN + GaN contact layers. During growth, pressure and flux ratio of all sources are kept constant for all samples. Only temperature of InGaN active layer is changed. These structures are analyzed with high-resolution X-ray diffraction (HR-XRD) technique. Their surface morphologies are investigated with atomic force microscopy (AFM). Reciprocal space mapping (RSM) is made different from classical HR-XRD analyses. Using this method, mixed peaks belonging to InGaN, AlGaN and GaN layers are seen more clearly and their full width at half maximum (FWHM) values is determined with better accuracy. With FWHM gained from RSM and Williamson-Hall (W-H) method based on universal elastic coefficients of the material, particle size D (nm), uniform stress σ (GPa), strain ε and anisotropic energy density u (kJ m -3 ) parameters for the samples are calculated. The results are compared with literature. On the other hand, to have an idea about the accuracy of the results AFM images are examined. Parameters calculated showed differences but it is seen that the largest particle size is gained for GaN and the smallest is gained for AlGaN. For all parameters, it is seen that they increase for GaN layer and decrease for AlGaN layer with increasing temperature. For InGaN layer parameters, they showed both increasing and decreasing or decreasing and increasing behavior harmonically with an increase in temperature. Results showed that they are compatible with literature. Results gained from Scherrer and W-H are very near to each other.

Karadeniz fen bilimleri dergisi, Dec 15, 2021

In this study Ag/TiO2/n-InP/Au structures are formed on 500 μm thick, (100) oriented n-InP semico... more In this study Ag/TiO2/n-InP/Au structures are formed on 500 μm thick, (100) oriented n-InP semiconductor having 3.13x10 18 cm -3 carrier density, by using sputtering method. TiO2 is grown as an interface with thickness of 60 Å. Some parameters of this structure are investigated in temperature range of 120-360 K. It is noticed that there are two linear regions in forward bias current-voltage (I-V) plot. These two regions are called as LBR (low bias region) and MBR(middle bias region). Richardson coefficient is determined and mean barrier height is calculated with double Gaussian distribution.

TiO2 Interface Instead of SiO2 in Terms of Dielectric Coefficient

Brazilian Journal of Physics, 2021

In this study, Ag/TiO2/n-InP/Au structure is formed by sputtering method and its reverse bias cha... more In this study, Ag/TiO2/n-InP/Au structure is formed by sputtering method and its reverse bias characterisation is made. n type InP semiconductor used in this study is 500 μm thick and has a carrier density of 3.13 × 1018 cm−3. Thickness of TiO2 interface layer is adjusted as 60 A. Some fundamental properties of the structure are investigated in a wide temperature range (120–360 K). Ln(Ir/Er) vs E0.5 plots are drawn by using reverse bias data. Barrier height and dielectric coefficient of TiO2 interfacial layer are determined. The importance of this study is, it discusses whether TiO2 can be used instead of SiO2 as an interfacial layer in Shottky barrier diodes or not. Also this study proves that dominant current conduction mechanism in Ag/TiO2/n-InP/Au structures can be explained with Frenkel-Poole emission or Schottky emission.

Politeknik Dergisi, 2021

In this study, three samples of GaN/AlInN/AlN/Al2O3 high electron mobility (HEMT) structures are ... more In this study, three samples of GaN/AlInN/AlN/Al2O3 high electron mobility (HEMT) structures are investigated with high resolution X-ray diffraction (HR-XRD) technique. Peak positions and peak broadenings are used in calculations, gained from rocking curves. Structural quality is determined from symmetric and asymmetric peak planes. Mosaic defects such as treadening dilocations (TDs), tilt and twist angles, lateral and vertical crystallite lengths are determined by using Williamson Hall (WH) method. In addition to these, surface morphology is also investigated by atomic force microscopy (AFM). It is noticed that crystal quality of epitaxial layers decrease in the order of samples C, B and A. Al compositions for samples A, B and C are found as %87.4, %86.6 and %86.4, respectively by using Vegard’s law.

Politeknik Dergisi, 2021

In this study structural and morphological properties of InGaN/GaN/Al2O3 structure, grown by Meta... more In this study structural and morphological properties of InGaN/GaN/Al2O3 structure, grown by Metal Organic Chemical Vapor Deposition (MOCVD) technique, is investigated. Crystal size of GaN in the structure is determined by using X-Ray Diffraction (XRD) techique. By the help of Raman spectra calibration coefficient is gained. This calibration coefficient and Termoelectric figure (ZT) of GaN is used to estimate number of stacks of GaN in the structure. Number of stacks (N) is a structural property and by using it an optical property, absorption coefficient, is determined. Using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) images total thickness of the sample is determined accurately and they are compared with each other. The sample used in this study is only for an example. The methods used in this study can be applied to different structures if right coefficients can be found. The importance of this study is that it plays a key role for determining structural,...

Journal of Materials Science: Materials in Electronics, 2019

In this study optical properties of InGaN/GaN/Al 2 O 3 multi-quantum well (MQW) structures are in... more In this study optical properties of InGaN/GaN/Al 2 O 3 multi-quantum well (MQW) structures are investigated in detail. Three samples containing InGaN/GaN/Al 2 O 3 MQWs are grown by using metal organic chemical vapor deposition technique. Sapphire (6H-Al 2 O 3) is used as the substrate. Forbidden energy band gaps (E g) of these three samples are determined from photoluminescence and absorption spectra. Results gained from these two spectra are compared with each other. It is found that E g values are between 2 and 3 eV. For determining refraction index, absorption coefficients, extinction coefficients and thickness of the films a rare method called Swanepoel envelope method is used. It is seen that results gained from this method are consistent with those in literature.

Gazi University Journal of Science Part A: Engineering and Innovation

Quick response is an important feature in design of optoelectronic cards. So in this study, struc... more Quick response is an important feature in design of optoelectronic cards. So in this study, structural properties of GaN/AlN/AlGaN HEMTs structures grown on sapphire by the chemical vapor adjustment method are analyzed by the X-ray diffraction method. The main property of these kind of materials is that they are resistant to high voltage, temperature, and pressure. Although their performance is worse compared silicon, for forcing limit standards, they present wide research field. In this study, the focus of investigation is dislocation density stemming from lattice mismatch between layers and wafer causing cracks on the surface. In HEMT structure calculation of dislocation density for GaN and AlN represents all structure. High dislocation density for AlN layer is determined because of aggressive behavior of Al element in the structure. Also, quantized GaN layers stop moving of dislocations and prevents surface cracks.

DergiPark (Istanbul University), Jun 18, 2021

In this study, the optical properties of AlInN/AlN high electron mobility transistor (HEMT) struc... more In this study, the optical properties of AlInN/AlN high electron mobility transistor (HEMT) structure, grown on c-oriented sapphire with Metal-Organic Chemical Vapor Deposition (MOCVD) technique, being investigated. Optical characterization is made Kubelka-Munk method. Transmittance, absorbance, and reflectance are investigated in detail. Also, the Kubelka-Munk theory is employed to determine the forbidden energy band gap of InN by using special functions. The energy band gap obtained by this method was compared.

Politeknik Dergisi, 2020

Structural properties of AlN buffer layers, grown by Metal Organic Chemical Vapor Deposition (MOC... more Structural properties of AlN buffer layers, grown by Metal Organic Chemical Vapor Deposition (MOCVD) on 4H-SiC substrate with thicknesses of 61.34, 116.88, 129.46 and 131.50 nm, are investigated by High Resolution X-Ray Diffraction (HR-XRD) technique. Interfacial roughness of AlN buffer layer was determined by XRR technique. The interface roughness value of 131.50 nm thick sample is determined as 0.50 nm. Mosaic defects, tilt angle, vertical and lateral coherence lengths are characterized by HR-XRD technique. The edge and screw dislocations of the 131.50 nm thick sample are found as 2.98x1010 and 8.86x108 cm-2 respectively. The results indicate that 131.50 nm thick AlN buffer layer should be used in order to gain high performance in optoelectronic terms in this study. Thus, optimization of AlN buffer layer thickness is extremely important in device performance.

Journal of Polytechnic, 2018

Structural properties of InGaN/GaN solar cells (SCs) grown by metal organic chemical vapor deposi... more Structural properties of InGaN/GaN solar cells (SCs) grown by metal organic chemical vapor deposition (MOCVD) technique are investigated by high resolution X-ray diffraction (HR-XRD) method. It is noticed that a-and c-lattice parameters of the structures showed small differences according to examined (hkl) planes. Fault percentage of the a-and c-lattice parameters are also calculated. It is seen that fault percentage is smaller than %2 for all samples. Investigations have been made for three different samples. Differences in crystal quality caused by growth conditions are seen in all three samples. At the same time, properties such as crystal size, strain and stress are determined. During determination of stress, two different methods including elastic constants, Young module and Poisson ratio are used. Results gained from these two methods are compared with each other. Thermal expansion coefficients of InGaN are calculated for (002), (004), (006) and (121) planes for 100 o C temperature difference (300-400 o C). It is seen that peak positions gained from HR-XRD are nearly the same with the ones in database. All the results obtained from calculations are given in tables in the following sections of this article. It can be seen that all these results are in accordance with previous works done by different authors and with the real values.

Silicon, 2021

In this study, structural and electrical properties of Ag/TiO2/n-InP/Au Schottky barrier diodes a... more In this study, structural and electrical properties of Ag/TiO2/n-InP/Au Schottky barrier diodes are investigated. Particle size, d-spacing, micro-strain, ideality factor and barrier heights of two samples are determined for two different interfacial TiO2 layer thickness. X-ray diffraction (XRD) and current-voltage (I-V) measurements are employed for mentioned parameters. It is seen that sample with 60 Å TiO2 interfacial layer is a more ideal diode. The reason for this is argued in main text and conclusion section.

Journal of Applied Physics, 2019

The effect of the TiO 2 interfacial layer on rectifying junction parameters of Ag/TiO 2 /n-InP/Au... more The effect of the TiO 2 interfacial layer on rectifying junction parameters of Ag/TiO 2 /n-InP/Au Schottky diodes has been investigated using current-voltage (I-V) measurements in the temperature range of 120-420 K with steps of 20 K. The barrier height is found to be 0.19 eV and 0.68 eV from current-voltage characteristics at 120 K and 420 K, respectively. At 120 K and 420 K, the ideality factor is found to be 3.52 and 1.01 for the Ag/TiO 2 /n-InP/Au Schottky barrier diode, respectively. These results are gained by the thermionic emission theory at room temperature. Values of series resistances gained from the Cheung-Cheung method are compared with results gained from a modified Norde method. These experimental results indicate that series resistance decreases with an increase in temperature. The current-voltage (I-V) measurements showed that the diode with the TiO 2 interfacial layer gave a double Gaussian property in the examined temperature range. The Richardson constant is also calculated from a modified Richardson plot and is found to be very compatible with the theoretical value. Interface state density is also examined by using I-V characteristics.

Karadeniz Fen Bilimleri Dergisi

In this study, dielectric properties of graded and non-graded InGaN/GaN multi quantum wells (MQWs... more In this study, dielectric properties of graded and non-graded InGaN/GaN multi quantum wells (MQWs), grown on sapphire(Al2O3) wafer by Metal Organic Chemical Vapor Deposition (MOCVD) technique, are investigated. In order to notice graded layer effect on characteristics of MQWs some of GaN layers are grown by doping In atoms. Dielectric function of films are determined by Swanepoel envelope method. Real and imaginer dielectric coefficient of the films are calculated by using refraction index and extinction coefficient. Differences in refraction index values are discussed for graded and non-graded samples. During determination of dielectric function variations of complex and imaginer dielectric coefficients with photon energy are shown for both samples

Karadeniz Fen Bilimleri Dergisi, 2021

Bu calismada, Metal organik kimyasal buhar biriktirme(MOCVD) metoduyla safir (Al2O3) uzerine buyu... more Bu calismada, Metal organik kimyasal buhar biriktirme(MOCVD) metoduyla safir (Al2O3) uzerine buyutulen dereceli ve derecesiz InGaN/GaN MQW’lerin dielektrik ozellikleri incelendi. Dereceli tabakanin MQW’nin karakteristikleri uzerine etkisini fark edebilmek icin bazi GaN tabakalar In asilanarak buyutulmustur. Filmlerin dielektrik fonksiyonu Swanepoel zarf metodu ile belirlenmistir. Filmlerin gercel ve imajiner dielektrik katsayilari, kirilma indisi ve sogurma katsayilari kullanilarak hesaplanmistir. Dereceli ve derecesiz ornekler icin kirilma indisi degerlerindeki farkliliklar tartisilmistir. Dielektrik fonksiyonunun belirlenmesi sirasinda, her iki numune icin kompleks ve imajiner dielektrik sabitlerinin foton enerjisine gore degisimleri gosterilmistir

In this study, X-ray diffraction peaks of Si, Ti, Au and ZnO grown on Ge substrate with thickness... more In this study, X-ray diffraction peaks of Si, Ti, Au and ZnO grown on Ge substrate with thickness of 500 nm by using sputtering method are analyzed to determine correlation length and dislocation density. It is seen that in most dense region of peaks, peak behaviour is in accordance with Gauss function. Right and left tails of peaks are in good accordance with q3 law. For randomized dislocations, obeying q3 law is typical and they can be monitored with w-scans by using open detectors. Whole profile is fitted with a limited dislocation dispersion. Edge dislocation density and correlation length are determined in the degree of 1010cm-2 and 103 nm, respectively. In order to gain these values, semi-experimental equations in Kragner method are used. For making a good fit, fit iteration step is taken as 9x106.

Swanepoel method for AlInN/AlN HEMTs

Journal of Materials Science: Materials in Electronics

Journal of Science and Technology of Dumlupınar University, Jan 15, 2016

Ag/TiOz/n-loPl Au Schottky bariyerli diyotlarm akun-voltaj karakteristikleri 300-400 K sicaklik a... more Ag/TiOz/n-loPl Au Schottky bariyerli diyotlarm akun-voltaj karakteristikleri 300-400 K sicaklik arahgmda incelendi. Metal ile yarriletken arasina 120 A kahnhg mda TiO, film tabakasi o lusturuldu. Diyotun ileri beslem akim-voltaj (1-V) karakteristiklerinden termiyonik emisyon modeline gore, sifir beslem bariyer yiiksekligi ve idealite faktoru parametreleri hesaplandi. Parametre lerin sicakhga bagh olarak degi §tigi ve sicakhk artarken bariyer yuksekliginin arttig t ve idealite faktorunun azaldig i goruldu.

Applied Physics A, Jan 18, 2019

In this study, three InGaN/GaN light-emitting diode (LED) structures with five periods are invest... more In this study, three InGaN/GaN light-emitting diode (LED) structures with five periods are investigated grown by metal organic chemical vapor deposition (MOCVD) technique. During growth of these three samples, active layer growth temperatures are adjusted as 650, 667 and 700 °C. These structures are grown on sapphire (Al 2 O 3 ) wafer as InGaN/GaN multiquantum wells (MQWs) between n-GaN and p-AlGaN + GaN contact layers. During growth, pressure and flux ratio of all sources are kept constant for all samples. Only temperature of InGaN active layer is changed. These structures are analyzed with high-resolution X-ray diffraction (HR-XRD) technique. Their surface morphologies are investigated with atomic force microscopy (AFM). Reciprocal space mapping (RSM) is made different from classical HR-XRD analyses. Using this method, mixed peaks belonging to InGaN, AlGaN and GaN layers are seen more clearly and their full width at half maximum (FWHM) values is determined with better accuracy. With FWHM gained from RSM and Williamson-Hall (W-H) method based on universal elastic coefficients of the material, particle size D (nm), uniform stress σ (GPa), strain ε and anisotropic energy density u (kJ m -3 ) parameters for the samples are calculated. The results are compared with literature. On the other hand, to have an idea about the accuracy of the results AFM images are examined. Parameters calculated showed differences but it is seen that the largest particle size is gained for GaN and the smallest is gained for AlGaN. For all parameters, it is seen that they increase for GaN layer and decrease for AlGaN layer with increasing temperature. For InGaN layer parameters, they showed both increasing and decreasing or decreasing and increasing behavior harmonically with an increase in temperature. Results showed that they are compatible with literature. Results gained from Scherrer and W-H are very near to each other.

Karadeniz fen bilimleri dergisi, Dec 15, 2021

In this study Ag/TiO2/n-InP/Au structures are formed on 500 μm thick, (100) oriented n-InP semico... more In this study Ag/TiO2/n-InP/Au structures are formed on 500 μm thick, (100) oriented n-InP semiconductor having 3.13x10 18 cm -3 carrier density, by using sputtering method. TiO2 is grown as an interface with thickness of 60 Å. Some parameters of this structure are investigated in temperature range of 120-360 K. It is noticed that there are two linear regions in forward bias current-voltage (I-V) plot. These two regions are called as LBR (low bias region) and MBR(middle bias region). Richardson coefficient is determined and mean barrier height is calculated with double Gaussian distribution.

TiO2 Interface Instead of SiO2 in Terms of Dielectric Coefficient

Brazilian Journal of Physics, 2021

In this study, Ag/TiO2/n-InP/Au structure is formed by sputtering method and its reverse bias cha... more In this study, Ag/TiO2/n-InP/Au structure is formed by sputtering method and its reverse bias characterisation is made. n type InP semiconductor used in this study is 500 μm thick and has a carrier density of 3.13 × 1018 cm−3. Thickness of TiO2 interface layer is adjusted as 60 A. Some fundamental properties of the structure are investigated in a wide temperature range (120–360 K). Ln(Ir/Er) vs E0.5 plots are drawn by using reverse bias data. Barrier height and dielectric coefficient of TiO2 interfacial layer are determined. The importance of this study is, it discusses whether TiO2 can be used instead of SiO2 as an interfacial layer in Shottky barrier diodes or not. Also this study proves that dominant current conduction mechanism in Ag/TiO2/n-InP/Au structures can be explained with Frenkel-Poole emission or Schottky emission.

Politeknik Dergisi, 2021

In this study, three samples of GaN/AlInN/AlN/Al2O3 high electron mobility (HEMT) structures are ... more In this study, three samples of GaN/AlInN/AlN/Al2O3 high electron mobility (HEMT) structures are investigated with high resolution X-ray diffraction (HR-XRD) technique. Peak positions and peak broadenings are used in calculations, gained from rocking curves. Structural quality is determined from symmetric and asymmetric peak planes. Mosaic defects such as treadening dilocations (TDs), tilt and twist angles, lateral and vertical crystallite lengths are determined by using Williamson Hall (WH) method. In addition to these, surface morphology is also investigated by atomic force microscopy (AFM). It is noticed that crystal quality of epitaxial layers decrease in the order of samples C, B and A. Al compositions for samples A, B and C are found as %87.4, %86.6 and %86.4, respectively by using Vegard’s law.

Politeknik Dergisi, 2021

In this study structural and morphological properties of InGaN/GaN/Al2O3 structure, grown by Meta... more In this study structural and morphological properties of InGaN/GaN/Al2O3 structure, grown by Metal Organic Chemical Vapor Deposition (MOCVD) technique, is investigated. Crystal size of GaN in the structure is determined by using X-Ray Diffraction (XRD) techique. By the help of Raman spectra calibration coefficient is gained. This calibration coefficient and Termoelectric figure (ZT) of GaN is used to estimate number of stacks of GaN in the structure. Number of stacks (N) is a structural property and by using it an optical property, absorption coefficient, is determined. Using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) images total thickness of the sample is determined accurately and they are compared with each other. The sample used in this study is only for an example. The methods used in this study can be applied to different structures if right coefficients can be found. The importance of this study is that it plays a key role for determining structural,...

Journal of Materials Science: Materials in Electronics, 2019

In this study optical properties of InGaN/GaN/Al 2 O 3 multi-quantum well (MQW) structures are in... more In this study optical properties of InGaN/GaN/Al 2 O 3 multi-quantum well (MQW) structures are investigated in detail. Three samples containing InGaN/GaN/Al 2 O 3 MQWs are grown by using metal organic chemical vapor deposition technique. Sapphire (6H-Al 2 O 3) is used as the substrate. Forbidden energy band gaps (E g) of these three samples are determined from photoluminescence and absorption spectra. Results gained from these two spectra are compared with each other. It is found that E g values are between 2 and 3 eV. For determining refraction index, absorption coefficients, extinction coefficients and thickness of the films a rare method called Swanepoel envelope method is used. It is seen that results gained from this method are consistent with those in literature.

Gazi University Journal of Science Part A: Engineering and Innovation

Quick response is an important feature in design of optoelectronic cards. So in this study, struc... more Quick response is an important feature in design of optoelectronic cards. So in this study, structural properties of GaN/AlN/AlGaN HEMTs structures grown on sapphire by the chemical vapor adjustment method are analyzed by the X-ray diffraction method. The main property of these kind of materials is that they are resistant to high voltage, temperature, and pressure. Although their performance is worse compared silicon, for forcing limit standards, they present wide research field. In this study, the focus of investigation is dislocation density stemming from lattice mismatch between layers and wafer causing cracks on the surface. In HEMT structure calculation of dislocation density for GaN and AlN represents all structure. High dislocation density for AlN layer is determined because of aggressive behavior of Al element in the structure. Also, quantized GaN layers stop moving of dislocations and prevents surface cracks.

DergiPark (Istanbul University), Jun 18, 2021

In this study, the optical properties of AlInN/AlN high electron mobility transistor (HEMT) struc... more In this study, the optical properties of AlInN/AlN high electron mobility transistor (HEMT) structure, grown on c-oriented sapphire with Metal-Organic Chemical Vapor Deposition (MOCVD) technique, being investigated. Optical characterization is made Kubelka-Munk method. Transmittance, absorbance, and reflectance are investigated in detail. Also, the Kubelka-Munk theory is employed to determine the forbidden energy band gap of InN by using special functions. The energy band gap obtained by this method was compared.

Politeknik Dergisi, 2020

Structural properties of AlN buffer layers, grown by Metal Organic Chemical Vapor Deposition (MOC... more Structural properties of AlN buffer layers, grown by Metal Organic Chemical Vapor Deposition (MOCVD) on 4H-SiC substrate with thicknesses of 61.34, 116.88, 129.46 and 131.50 nm, are investigated by High Resolution X-Ray Diffraction (HR-XRD) technique. Interfacial roughness of AlN buffer layer was determined by XRR technique. The interface roughness value of 131.50 nm thick sample is determined as 0.50 nm. Mosaic defects, tilt angle, vertical and lateral coherence lengths are characterized by HR-XRD technique. The edge and screw dislocations of the 131.50 nm thick sample are found as 2.98x1010 and 8.86x108 cm-2 respectively. The results indicate that 131.50 nm thick AlN buffer layer should be used in order to gain high performance in optoelectronic terms in this study. Thus, optimization of AlN buffer layer thickness is extremely important in device performance.

Journal of Polytechnic, 2018

Structural properties of InGaN/GaN solar cells (SCs) grown by metal organic chemical vapor deposi... more Structural properties of InGaN/GaN solar cells (SCs) grown by metal organic chemical vapor deposition (MOCVD) technique are investigated by high resolution X-ray diffraction (HR-XRD) method. It is noticed that a-and c-lattice parameters of the structures showed small differences according to examined (hkl) planes. Fault percentage of the a-and c-lattice parameters are also calculated. It is seen that fault percentage is smaller than %2 for all samples. Investigations have been made for three different samples. Differences in crystal quality caused by growth conditions are seen in all three samples. At the same time, properties such as crystal size, strain and stress are determined. During determination of stress, two different methods including elastic constants, Young module and Poisson ratio are used. Results gained from these two methods are compared with each other. Thermal expansion coefficients of InGaN are calculated for (002), (004), (006) and (121) planes for 100 o C temperature difference (300-400 o C). It is seen that peak positions gained from HR-XRD are nearly the same with the ones in database. All the results obtained from calculations are given in tables in the following sections of this article. It can be seen that all these results are in accordance with previous works done by different authors and with the real values.

Silicon, 2021

In this study, structural and electrical properties of Ag/TiO2/n-InP/Au Schottky barrier diodes a... more In this study, structural and electrical properties of Ag/TiO2/n-InP/Au Schottky barrier diodes are investigated. Particle size, d-spacing, micro-strain, ideality factor and barrier heights of two samples are determined for two different interfacial TiO2 layer thickness. X-ray diffraction (XRD) and current-voltage (I-V) measurements are employed for mentioned parameters. It is seen that sample with 60 Å TiO2 interfacial layer is a more ideal diode. The reason for this is argued in main text and conclusion section.

Journal of Applied Physics, 2019

The effect of the TiO 2 interfacial layer on rectifying junction parameters of Ag/TiO 2 /n-InP/Au... more The effect of the TiO 2 interfacial layer on rectifying junction parameters of Ag/TiO 2 /n-InP/Au Schottky diodes has been investigated using current-voltage (I-V) measurements in the temperature range of 120-420 K with steps of 20 K. The barrier height is found to be 0.19 eV and 0.68 eV from current-voltage characteristics at 120 K and 420 K, respectively. At 120 K and 420 K, the ideality factor is found to be 3.52 and 1.01 for the Ag/TiO 2 /n-InP/Au Schottky barrier diode, respectively. These results are gained by the thermionic emission theory at room temperature. Values of series resistances gained from the Cheung-Cheung method are compared with results gained from a modified Norde method. These experimental results indicate that series resistance decreases with an increase in temperature. The current-voltage (I-V) measurements showed that the diode with the TiO 2 interfacial layer gave a double Gaussian property in the examined temperature range. The Richardson constant is also calculated from a modified Richardson plot and is found to be very compatible with the theoretical value. Interface state density is also examined by using I-V characteristics.

Karadeniz Fen Bilimleri Dergisi

In this study, dielectric properties of graded and non-graded InGaN/GaN multi quantum wells (MQWs... more In this study, dielectric properties of graded and non-graded InGaN/GaN multi quantum wells (MQWs), grown on sapphire(Al2O3) wafer by Metal Organic Chemical Vapor Deposition (MOCVD) technique, are investigated. In order to notice graded layer effect on characteristics of MQWs some of GaN layers are grown by doping In atoms. Dielectric function of films are determined by Swanepoel envelope method. Real and imaginer dielectric coefficient of the films are calculated by using refraction index and extinction coefficient. Differences in refraction index values are discussed for graded and non-graded samples. During determination of dielectric function variations of complex and imaginer dielectric coefficients with photon energy are shown for both samples

Karadeniz Fen Bilimleri Dergisi, 2021

Bu calismada, Metal organik kimyasal buhar biriktirme(MOCVD) metoduyla safir (Al2O3) uzerine buyu... more Bu calismada, Metal organik kimyasal buhar biriktirme(MOCVD) metoduyla safir (Al2O3) uzerine buyutulen dereceli ve derecesiz InGaN/GaN MQW’lerin dielektrik ozellikleri incelendi. Dereceli tabakanin MQW’nin karakteristikleri uzerine etkisini fark edebilmek icin bazi GaN tabakalar In asilanarak buyutulmustur. Filmlerin dielektrik fonksiyonu Swanepoel zarf metodu ile belirlenmistir. Filmlerin gercel ve imajiner dielektrik katsayilari, kirilma indisi ve sogurma katsayilari kullanilarak hesaplanmistir. Dereceli ve derecesiz ornekler icin kirilma indisi degerlerindeki farkliliklar tartisilmistir. Dielektrik fonksiyonunun belirlenmesi sirasinda, her iki numune icin kompleks ve imajiner dielektrik sabitlerinin foton enerjisine gore degisimleri gosterilmistir

In this study, X-ray diffraction peaks of Si, Ti, Au and ZnO grown on Ge substrate with thickness... more In this study, X-ray diffraction peaks of Si, Ti, Au and ZnO grown on Ge substrate with thickness of 500 nm by using sputtering method are analyzed to determine correlation length and dislocation density. It is seen that in most dense region of peaks, peak behaviour is in accordance with Gauss function. Right and left tails of peaks are in good accordance with q3 law. For randomized dislocations, obeying q3 law is typical and they can be monitored with w-scans by using open detectors. Whole profile is fitted with a limited dislocation dispersion. Edge dislocation density and correlation length are determined in the degree of 1010cm-2 and 103 nm, respectively. In order to gain these values, semi-experimental equations in Kragner method are used. For making a good fit, fit iteration step is taken as 9x106.

Swanepoel method for AlInN/AlN HEMTs

Journal of Materials Science: Materials in Electronics