M.R. Hashim

Enhanced optical performance of electrochemically etched porous silicon carbide

Porous silicon carbide (PSC) was successfully synthesized via electrochemical etching of an n-type hexagonal silicon carbide (6H-SiC) substrate using various current densities. The cyclic voltammograms of SiC dissolution show that illumination is required for the accumulation of carriers at the surface, followed by surface oxidation and dissolution of the solid. The morphological and optical characterizations of PSC were reported. Scanning electron microscopy results demonstrated that the current density can be considered an important etching parameter that controls the porosity and uniformity of PSC; hence, it can be used to optimize the optical properties of the porous samples.

Preparation of p-type Na-doped Cu2O by electrodeposition for a p-n homojunction thin film solar cell

In this work, a method of enhancing the electrical properties of the electrodeposited p-type Cu2O film is described. Sodium doped Cu2O was achieved by adding sodium aluminate complex solution to the electrodeposition alkaline Cu (II) lactate electrolyte. The optimal Na content [Na at% atomic ratio] incorporated in the Cu2O film was found to be approximately 1.34 at.%. The XPS result shows that the binding energy at 1072.4 ± 0.2 eV corresponds to the presence of sodium in sodium oxide. The optimized resistivity and the hole concentration were approximately 291 Ω cm and 2.13 × 1018 cm3, respectively. A Cu2O p-n homojunction solar cell with 2.05% efficiency was fabricated using a Cl-doped n-type Cu2O film and an optimized Na-doped Cu2O film.

Effect of growth time on Ti-doped ZnO nanorods prepared by low-temperature chemical bath deposition

Ti-doped ZnO nanorod arrays were grown onto Si substrate using chemical bath deposition (CBD) method at 93 °C. To investigate the effect of time deposition on the morphological, and structural properties, four Ti-doped ZnO samples were prepared at various deposition periods of time (2, 3.5, 5, and 6.5 h). FESEM images displayed high-quality and uniform nanorods with a mean length strongly dependent upon deposition time; i.e. it increases for prolonged growth time. Additionally, EFTEM images reveal a strong erosion on the lateral side for the sample prepared for 6.5 h as compared to 5 h. This might be attributed to the dissolution reaction of ZnO with for prolonged growth time. XRD analysis confirms the formation of a hexagonal wurtzite-type structure for all samples with a preferred growth orientation along the c-axis direction. The (100) peak intensity was enhanced and then quenched, which might be the result of an erosion on the lateral side of nanorods as seen in EFTEM. This study confirms the important role of growth time on the morphological features of Ti-doped ZnO nanorods prepared using CBD.

The effects of TiO2 in ZnO nanorod arrays by chemical bath deposition

ZnO and TiO2 doped ZnO nanorod arrays have been synthesized using simple, low temperature and inexpensive chemical bath deposition procedures on silicon substrates. The FESEM results showed high-quality nanorods uniformly grown on the substrate surfaces. No defects issues were observed at the nanorods surface. The XRD patterns confirmed that the prepared samples possessed hexagonal wurtzite structure with preferred growth in the c-axis direction. The doped sample exhibited high (002) intensity with slight shifting towards the low angle in comparison with pure ZnO. The optical properties studied using PL system exhibited a strong enhancement in near band edge emission with blue-shifting in the doped sample as compared with pure ZnO. In addition, the visible emission in the doped structure was enhanced in comparison with ZnO. All the results of doped sample confirmed that the TiO2 can play a vital role in the improvement the physical properties of ZnO nanorods prepared using low temperature, inexpensive, and simple chemical bath deposition method on silicon substrates.

Simulation of optimum parameters for GaN MSM UV photodetector

In this study the optimum parameters of GaN M-S-M photodetector are discussed. The evaluation of the photodetector depends on many parameters, the most of the important parameters the quality of the GaN film and others depend on the geometry of the interdigited electrode. In this simulation work using MATLAB software with consideration of the reflection and absorption on the metal contacts, a detailed study involving various electrode spacings (S) and widths (W) reveals conclusive results in device design. The optimum interelectrode design for interdigitated MSM-PD has been specified and evaluated by effect on quantum efficiency and responsivity.

The Effects Of Slanted Mesa Sidewall On P‐N Junction GaN‐Based LEDs

Typically, most of the commercially available GaN‐based LEDs (Light Emitting Diodes) are grown on sapphire as their substrates. Due to the insulating substrate, lateral current injection is employed so that the anode and cathode contacts are in side‐by‐side configuration. During the etching process, the possibility of slanted mesa sidewall to form is higher. In this work, the influence of slanted mesa sidewall are studied while its light emitting area size and contacts position are maintained. The comparison for optical output power, current‐voltage, thermal dissipation and distribution characteristics of different angles of slanted mesa sidewall are performed. Angles of slanted mesa sidewall are varied from angle‐in and angle‐out with reference to 90° at mesa edge. The simulation results revealed that with the increment of slanted angle, the LEDs performed better due to improved overall emission intensity and uniform current distribution of the devices. The angled sidewalls efficiently deflect photons th...