Y. Özen

Microstructural defect properties of InGaN/GaN blue light emitting diode structures

In this paper, we study structural and morphological properties of metal-organic chemical vapour deposition-grown InGaN/GaN light emitting diode (LED) structures with different indium (In) content by means of high-resolution X-ray diffraction, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) and current–voltage characteristic (I–V). We have found out that the tilt and twist angles, lateral and vertical coherence lengths of mosaic blocks, grain size, screw and edge dislocation densities of GaN and InGaN layers, and surface roughness monotonically vary with In content. Mosaic defects obtained due to temperature using reciprocal lattice space map has revealed optimized growth temperature for active InGaN layer of MQW LED. It has been observed in this growth temperature that according to AFM result, LED structure has high crystal dimension, and is rough whereas according to PL and FTIR results, bandgap energy shifted to blue, and energy peak half-width decreased at high values. According to I–V measurements, it was observed that LED reacted against light at optimized temperature. In conclusion, we have seen that InGaN MQW structure’s structural, optical and electrical results supported one another.

Study on growth and characterizations of GaxIn1−xP/GaAs solar cell structure

GaxIn1−xP/GaAs solar cell (SC) structure was grown on p-type (100)-oriented GaAs substrate by using solid-source molecular beam epitaxy technique. The structural, optical and morphological properties of GaxIn1−xP/GaAs SC structure have been evaluated by means of high resolution X-ray diffraction, photoluminescence, spectroscopic ellipsometry and atomic force microscopy measurements at room temperature. In addition, GaxIn1−xP/GaAs SC structure was fabricated for obtaining the cell’s electrical output parameters. For this purpose, the current–voltage characteristics of GaxIn1−xP/GaAs SC structure were performed and analyzed at the room temperature under both dark and illuminations by using air mass global 1.5 (AM1.5) solar simulator. The device parameters such as the open-circuit voltage, the short-circuit current (Isc), the fill factor and the energy convertion efficiency (η) of GaxIn1−xP/GaAs SC structure were extracted from the current–voltage characteristics.

Structural, optical and electrical characterization of dilute nitride GaP1−x−yAsyNx structures grown on Si and GaP substrates

The structural, optical and electrical properties of dilute nitride p–n junction GaP1−x−yAsyNx structures grown on n-type GaP (100) and n-type Si (100) misoriented by 4° towards the [110] direction substrates were studied. These properties of the samples, which were grown by using molecular beam epitaxy (MBE) technique, were investigated by using high-resolution X-Ray diffraction (HRXRD), energy dispersive X-Ray (EDX), room temperature photoluminescence (PL) and current–voltage (I–V) measurements. Both alloy composition values (x, y) and crystal structure parameters were determined from HRXRD measurements while the band gap energies were obtained from PL measurements. Composition values were also determined by using EDX measurements and compared with HRXRD results. The better crystal quality was found for the sample grown on GaP substrate from both the HRXRD and PL results. In addition, the theoretical band gap energies calculated from the band anticrossing (BAC) model and experimental band gap energies determined from the PL measurements were compared and found to be in good agreement with each other. The p–n junction GaP1−x−yAsyNx/GaP (Si) diode devices were fabricated to investigate their electrical properties. The I–V characteristics of diodes were analyzed at room temperature and the diode formed on GaP substrate exhibited better results compared to other diode.

Preparation of RF sputtered AZO/Au thin film hydrogen peroxide sensitive electrode for utilization as a biosensor

Abstract In this study, hydrogen peroxide (H2O2) sensitive Al doped ZO(AZO)/Au thin film electrode has been developed for the utilization as a biosensor. A preferred c-axis oriented AZO/Au thin film was deposited on quartz substrate by RF magnetron sputtering at room temperature. Structural, morphological and optical properties of the AZO film were analyzed by X-ray diffraction, atomic force microscopy and photoluminescence. The sensor performance was characterized by electrochemical analysis device. The sensibility of prepared thin film electrodes to H2O2 was studied. The dependence of amperometric response current on the glucose and cholesterol concentrations was also investigated.