Effect of indium doping on the electrical and structural properties of TiO2 thin films used in MOS devices

We investigated the effect of Indium (In) doping on the structural and electrical properties of Ti/Au/ TiO2:In/n-Si metal-oxide-semiconductor (MOS) devices. Sputtering grown TiO2 thin films on Si substrate were doped using two In-films with 15 nm and 50 nm thicknesses leading to two structures named Low Indium Doped (LID) sample and High Indium Doped (HID) sample, respectively. XRD analysis shows no diffraction pattern related to Indium indicating that In has been incorporated into the TiO2 lattice. Current-Voltage (I-V) characteristics show that rectification ratio at 2V is higher for HID sample than for LID sample. Evaluated barrier height, ϕB0 , decreased while the ideality factor, n, increased with decreasing temperature. Such behavior is ascribed to barrier inhomogeneity that was assumed to have a Gaussian Distribution (GD) of barrier heights at interface. Evidence of such GD was confirmed by plotting ϕB0versus n. High value of mean barrier ϕ̅B0 and lower value of standard deviation (σ) of HID structure are due to indium doping which increases the barrier homogeneities. Finally, estimated Richardson constants A* are in good agreement with theoretic values (112 A/cm2K2), particularly, for the HID structure

The role of defects on the performance of quantum dot intermediate band solar cells

Electrically active defects present in three InAs/GaAs quantum dots (QDs) intermediate band solar cells grown by metalorganic vapor phase epitaxy have been investigated. The devices’ structures are almost identical, differing only in the growth temperature and thickness of the GaAs layers that cover each InAs QD layer. These differences induce significant changes in the solar energy conversion efficiency of the photovoltaic cells, as previously reported. In this work, a systematic investigation was carried out using deep level transient spectroscopy (DLTS) and Laplace DLTS measurements on control samples and solar cell devices, which have clearly shown that electrically active traps play an important role in the device figures of merit, such as open circuit voltage, short circuit current, and shunt resistance. In particular, it was found that the well-known EL2 defect negatively affects both the open circuit voltage and shunt resistance, more in structures containing QDs, as a consequence of the temperature cycle required to deposit them. Other unidentified defects, that are absent in samples in which the QDs were annealed at 700 °C, contribute to a reduction of the short circuit current, as they increase the Shockley-Read-Hall recombination. Photoluminescence results further support the DLTS-based assignments

Effect of erbium-doping concentration on the electrical, structural and morphological properties of heterostructures based on TiO2 thin films

Effect of erbium (Er) doping on the electrical, structural and morphological properties of TiO2 thin films deposited by the combination of a simple sol–gel process and spin-coating technique on p-type silicon substrates, has been investigated. A systematic study of the effect of concentration of Er on the properties of heterostructures was carried out. Raman spectroscopy and atomic force microscopy have been used to study the structural and morphology properties of devices based on Er-doped TiO2/Si heterostructures. Deep level transient spectroscopy (DLTS) has been also employed to study the electrically active defects within the band gap of Er-doped TiO2 thin films. DLTS that has proved to be a powerful tool in analysing traps in semiconductors devices showed that undoped TiO2-based devices exhibit five defects. However, three defects have been detected in the low erbium-doped TiO2 devices and only one defect was observed in the higher erbium-doped devices. These results provide strong evidence that Er doping annihilates oxygen-related defects and demonstrate the effective proof of doping process in TiO2 thin film. This finding contributes to the improved activities (e.g., photocatalytic) of TiO2 since the increase in charge traps can reduce bulk recombination and consequently, separates photogenerated electrons and holes more efficiently. Furthermore, it is found that the overall electrical properties of the devices are improved by increasing Er doping concentration. This study provides an important understanding of the deep and shallow level defects in Er-doped TiO2 thin films, which is essential for the manufacturing of future devices including UV detectors

Effect of growth techniques on the structural, optical and electrical properties of indium doped TiO2thin films

We have investigated the effect of the growth techniques on the structural, the electrically and optically active defects in Indium doped TiO2 thin films grown by pulsed laser deposition (PLD) and sputtering techniques. X-ray diffraction (XRD) and Raman spectroscopy patterns revealed both rutile and anatase phases for the sputtering samples. On the other hand, only the anatase phase was observed for the PLD samples. The photoluminescence (PL) spectra have unveiled several peaks which were explained by defect related optical transitions. Particularly, the PL bands are fully consistent with anatase/rutile TiO2 phases and the formation of In2O3 during the preparation of our samples. It was also observed that at −4 V reverse bias, the PLD samples have lower leakage currents (∼1.4 × 10−7 A) as compared to the sputtering samples (∼5.9 × 10−7 A). In addition, the PLD samples exhibited lower ideality factors and higher barrier heights as compared to those grown by sputtering. Finally, the Deep Level Transient Spectroscopy (DLTS) measurements have shown only one defect in the PLD samples whereas five defects have been detected in the sputtering samples. Therefore, our results provide strong evidence that the PLD technique is better suited for the growth of In-doped TiO2 thin films

Structural, Optical and Electrical Properties of Self-Assembled InAs Quantum Dots Based p–i–n Devices Grown on GaAs Substrate by Molecular Beam Epitaxy for Telecommunication Applications

This work aims to investigate the structural, electrical, and optical properties of InAs quantum dots (QDs) grown by Molecular Beam Epitaxy on GaAs substrates. As-made samples were thoroughly characterized using different techniques, including Atomic Force Microscopy (AFM), X-ray diffraction (XRD), and highresolution X-ray diffraction (HRXRD). The patterns of HRXRD revealed an excellent crystallinity of the nanostructure with a maximum diameter of 25 nm as demonstrated by AFM images. The photoluminescence (PL) spectra showed two distinct bands centered at 835 and 1210 nm, and the intensity of these wavelengths increased with decreasing temperature. A redshift accompanied by a decrease in the FWHM as a function of temperature was observed as a consequence of the thermal escape of carriers. The Ideality factor (n), built-in potential energy, and series resistance at different temperatures were also determined from current-voltage characteristics curves

3D nanosheet networks like mesoporous structure of NiO/CoSe2nanohybrid directly grown on nickel foam for oxygen evolution process

The advancement of energy conversion and storage frameworks depends significantly on the development of reliable, effective, and affordable electrocatalysts. Steadily, there is an increasing demand of energy, fossil fuels consumption, and alarming environmental issues that have induced researchers to find alternate renewable sources. For this purpose, water splitting using various electrocatalysts have been investigated in a highly favourable virtual environment and is a highly demanding challenge to fulfil the energy crises. Here in this work, we fabricated three-dimensional (3D) nanosheet network NiO/CoSe2/NF nanocomposite (where NF represents nickel foam) material via hydrothermal treatment. All the synthesized materials like NiO/NF, CoSe2/NF, and NiO/CoSe2/NF nanohybrid are tested for the oxygen evolution process in a basic medium (1.0M KOH). Among all directly grown NiO/CoSe2 3D nanosheet has shown the lowest overpotential (263 mV), Tafel slope value (38 mVdec−1), which is remarkably improved as compared to the pristine NiO/NF and CoSe2. The resultant enhanced performance is due to improved morphological characteristics, increased surface area, and electrochemical coupling of electrons between NiO/NF and CoSe2/NF due to the synergistic effect

Effects of Gamma Radiation on the Electrical Properties of InAs/InGaAs Quantum Dots Based Laser Structures Grown on GaAs and Si Substrates by Molecular Beam Epitaxy

This study investigates the impact of gamma radiation on the electrical properties of InAs/InGaAs quantum dots based laser structures grown on both GaAs (Sample A) and Si (Sample B) substrates using molecular beam epitaxy. The research explores the electrical characteristics of the lasers before and after being exposed to gamma radiation employing Current - Voltage (I-V), Capacitance - Voltage (C-V), Deep Level Transient Spectroscopy (DLTS) and Laplace DLTS techniques. The results show that the electrical properties of the lasers change due to gamma radiation exposure, and the extent of the change depends on the substrate used for growth. The I–V results revealed that the ideality factor (n) and built-in voltage were increased in Sample A and Sample B after radiation. Nonetheless, the series resistance (Rs) at room temperature decreased in both samples after radiation. Overall, this study provides valuable insights into the effects of gamma radiation on the electrical properties of InAs/InGaAs quantum dots lasers and highlights the importance of considering substrate materials in the design of radiation-hardened electronic devices