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    Effect of Si-doped and undoped inter-layer transition time on the strain-compensated InGaAs/InAlAs QCL active region grown with MOVPE
    (Elsevier B.V., 2023) Perkitel, Izel; Demir, Ilkay
    In this study, we report the effect of the combination of Si-doped and undoped inter-layer transition time in the strain compensated In0.67Ga0.33As/In0.36Al0.64As quantum cascade laser (QCL) structure grown on InP substrate by Metal Organic Vapor Phase Epitaxy (MOVPE). In situ reflectance spectroscopy and high resolution X-ray diffraction (HRXRD) technique have been used for the analysis of growth steps and crystalline quality of QCL structures, respectively. In addition, since thickness accuracy is very important for QCLs, two different thickness calculation methods have been used in the Global Fit simulation program for detailed thickness accuracy of structures. As a result, optimum values for thickness accuracy have been obtained as 5 and 10 s between undoped and Si-doped layers, respectively, as verified by the two methods. © 2022 Elsevier B.V.
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    Influence of Highly Efficient Carbon Doping on AlxGa1-xAs Layers with Different Al Compositions (x) Grown by MOVPE
    (Springer, 2023) Perkitel, Izel; Kekul, Reyhan; Altuntas, Ismail; Gur, Emre; Demir, Ilkay
    Carbon (C)-doped aluminum gallium arsenide (AlxGa1-xAs) epitaxial layers with different aluminum (Al) concentrations have been grown on gallium arsenide (GaAs) substrates by metalorganic vapor phase epitaxy (MOVPE) technique. The impact of varying carbon tetrabromide (CBr4) flow rates on the electrical properties of AlxGa1-xAs materials with different Al compositions has been investigated. High-resolution x-ray diffraction (HRXRD) measurement and a Hall effect measurement system have been used to determine the Al compositions and to evaluate the electrical properties. It has been found that the carrier density increases and the mobility decreases by increasing the flow rate of CBr4 and changing Al compositions up to a certain point. In contrast, at higher Al compositions, a decrease in carrier density and an increase in mobility have been observed with increasing CBr4 flow rate. Since these observed trends require to be analyzed in more detail, x-ray photoelectron spectroscopy (XPS) has been used to analyze the elements in the structure. From the XPS results, it has been shown that the atomic concentration of the arsenic in the structure decreased with the increase in CBr4 flow rates. In addition, it has been shown that the Al composition in the AlxGa1-xAs material obtained from the XRD results increases with the increase in the atomic concentration of the arsenic. Accordingly, a linear increase in carrier concentration is shown with increasing Al composition. This increase is explained by the effect of the Al-C bond content on the electrical properties of Al(x)Ga(1-)xAs.
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    The Effect of Si (111) Substrate Surface Cleaning on Growth Rate and Crystal Quality of MOVPE Grown AlN
    (Gazi Univ, 2022) Perkitel, Izel; Altuntas, Ismail; Demir, Ilkay
    In this work, the effect of Si (111) substrate surface cleaning by RCA (Radio Corporation of America) method on growth rate and crystalline quality of epitaxially grown AlN thin films by MOVPE (Metal Organic Vapor Phase Epitaxy) technique is investigated. In situ reflectance system and high resolution X-ray diffraction (HRXRD) technique are used for the analysis of growth rate and crystal quality of epitaxial AlN layers, respectively. Also, The Raman measurement is done to show the effect of the RCA cleaning procedure on the position of the peaks that occurred in the Raman spectra. The results have shown that the surface cleaning of Si (111) substrate by the RCA method removes the oxide layer formed on the surface, also helps to decrease the parasitic reactions and increases the adatom efficiency, results in an increased growth rate of the AlN layer. Besides, surface cleaning of Si (111) substrate by the RCA method has reduced the FWHM value similar to 5% for omega-2 theta scan and similar to 60% for omega scan of AlN epilayer, indicating an improvement in crystal quality.