Structural And Optical Studies Of Wide Band-Gap AlxGa1-xN (0 ≤ x ≤ 1) Semiconductors [TK7871.85. N577 2007 f rb].

Tujuan projek ini ialah untuk mengkaji ciri struktur dan optik bagi semikonduktor-semikondutor berjurang tenaga lebar AlxGa1-xN (0 ≤ x ≤ 1) dengan pelbagai peralatan pencirian yang tak bersentuhan dan tak memusnahkan. The aim of this project is to study the structural and optical properties of wide band gap AlxGa1-xN (0 ≤ x ≤ 1) semiconductors by means of various non-contact and non-destructive characterization tools

X-Ray Diffraction Analysis Of Gallium Oxide Thin Films Synthesized By A Simple And Cost-Effective Method

Wide energy gap beta type gallium oxide (Ga2O3) semiconductor material has attracted many researchers’ interests due its thermal and chemical stability. For synthesising Ga2O3 thin films, sol-gel spin coating is a simple and cost-efficient method, especially for spin coating on cheap substrate such as silicon (Si) substrate. However, little is known about the spin coating growth of the Ga2O3 thin films on Si substrate. In this paper, special attention was paid to the pre-treatment of the Si substrate and the coated layer prior and post spin coating because the uniformity and the quality of the synthesized films are strongly affected by the surface conditions of the substrate/layer. To access the structural and crystallite quality of the deposited Ga2O3, X-ray diffraction measurements were carried out and in-depth analyses using Williamson-Hall and size-strain plots methods were performed. The results show that the crystallite size of the spin coated Ga2O3 on Si is not influenced by the micro strain

Effect of Surfactant Concentrations on the Properties of Sol-Gel Spin Coated GaN Thin Films

We report on the effects of different surfactant concentrations on the properties of gal lium nitride (GaN) thin films grown on si licon substrate by so l-gel spin coati ng method. The precursor so lution was prepared using gallium nitrate hydrate powder as starting material. ethano l, diethanolamine (DEA) and distilled water were used as so lvent and stabi lizer, respectively. DitTerent molar ratios of DEA to gallium nitrate hydrate (i.e. , 1: I, 2:1 and 3: I) were used. The crystal structure and orientation of the films were analyzed by X-ray diffraction technique (XRD). The XRD results revealed that a ll the deposited films with different surfactant concentrations have wurtzite structure and with GaN(002) preferred orientation. Field-emission scanning electron microscopy showed that GaN thin films with uniform and packed grain thin tilm were tormed. Energy dispersive X-ray spectroscopy show that the present of gallium, nitrogen, oxygen and si licon. The optical study was investigated by Fourier transform infrared spectroscopy and the transverse and longitudinal phonon modes of wurtzite GaN were clearly identified from the films prepared under various surfactant concentrations. All the results reveal that the concentration of surfactant plays an important role tor quality of GaN thin films

Sol–Gel Spin Coating Growth of Magnesium-Doped Indium Nitride Thin Films on Different Substrates

We report on the growth of p-type indium nitride (InN) thin films on different substrates using a relatively simple and cost-effective sol-gel spin coating method. The precursors for the indium source and p-type dopant were indium nitrate hydrate and magnesium chloride 6-hydrate powders, respectively. The structural, morphology, and optical properties of p-type InN thin films grown on different substrates were investigated. X-ray diffraction patterns revealed that the deposited Mg-doped InN thin film on GaN/AlN/Si(111) template show polycrystalline wurtzite structure with a strong InN(002) orientation and have a good crystallinity. Field emission scanning electron microscopy images and energy dispersive X-ray results showed that all the films exhibit densely packed surface morphology with hexagonal-like grains shape and low oxygen percentage with almost 1:1 ratio of indium to nitrogen. Moreover, two Raman-active modes of E2(High) and A1(LO) of the wurtzite InN were clearly observed for all samples. The ultraviolet-visible-near infrared spectroscopy results showed that the energy bandgap of the Mg-doped InN thin films was in the range of 1.62-1.66 eV. From all the results, it can be concluded that the Mg doped InN film on GaN/AlN/Si(111) substrate has better crystalline quality as compared to that of other substrates

Comparative Study of Gas Ratio on Indium Nitride Thin Films Grown on Flexible Substrates Prepared by Reactive Sputtering Method

In this report, indium nitride thin fi lms were deposited on kapton polyimide flexible substrate by reactive radio frequency (RF) sputtering method using an indium target in a mixture of Ar and N2 gases. The InN thin films were deposited under different gas ratio, i.e 90:10, 80 20, 70 30 and 6040 of N2 Ar The crystalline structures, surface morphologies, elemental composition and electrical properties of the deposited films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy and hall effect The X-ray diffraction revealed wurtzite polycrystalline with hexagonal InN (002), (101), (102), (1 03) and (201) preferred growth orientation. The morphologies showed smooth and uniform surface of gas ratio at 6040 compare to others gas ratio. In overall, the characteristics of the InN thin films were effectively improved with combination the N2 Argas ration at 6040. The results showed that the gas ratio plays an important role in improving the properties of the InN thin films

UV Photodetector based on Mg-doped GaN Thin Films Prepared by Sol-gel Spin Coating

In this work, sol-gel spin coated 2 % of magnesium (Mg) doped gallium nitride (GaN) thin films grown on AIN sapphire substrate was reported. The structural, lattice vibrational, and electrical properties of the deposited films were investigated and compared. X-ray diffraction results show that the hexagonal wurtzite structure with preferred orientation of GaN(002). The Raman active phonon modes of the wurtzite GaN correspond to the E2(high) and A1(LO) at 568 em 1 and 733 em 1 phonon modes of the hexagonal GaN were observed, while a broad peak attributed to the Mg-related lattice vibrational mode was detected at 669 em 1. Hall effects results show that the resistivity of 0.1397 0 em for the Mg-doped GaN. The carrier concentration and hall mobility of 1.77 x 1018 cm3 and 6.04 cm2/Vs were obtained. Besides, the characteristics of dark and photocurrent of the ultraviolet (UV) detector and the UV photoresponse of the detector were investigated. The measurements were conducted under dark and UV illuminations. The current-voltage (1-V) characteristics of the Mg doped GaN-based UV photodetector exhibits tile Schottky behaviour. Lastly, the ideality factor and Schottky barrier heights were calculated using thermionic emission theory

Low-cost Growth of Magnesium Doped Gallium Nitride Thin Films by Sol-Gel Spin Coating Method

Low-cost sol-gel spin coating growth of magnesium (Mg) doped gallium nitride (GaN) thin films with different concentrations of Mg was reported. The effects of the Mg concentration on the structural, surface morphology, elemental compositions, lattice vibrational, and electrical properties of the deposited films were investigated. X-ray diffraction results show that the Mg-doped samples have wurtzite structure with preferred orientation of GaN(002). The crystallite size decreases and the surface of the films with pits/pores were formed, while the crystalline quality of the films degraded as the Mg concentration increases from 2% to 6. %. All the Raman active phonon modes of the wurtzite GaN were observed while a broad peak attributed to the Mg-related lattice vibrational mode was detected at 669 cm-1 . Hall effect results show that the resistivity of the thin films decreases while the hole concentration and hall mobility of thin films increases as the concentration of the Mg increase

Effects Of Different Amounts Of Surfactant On Characteristics Of Sol-Gel Dip Coated Gallium Nitride Thin Films

- In the present study, sol-gel dip coating method was used to synthesize gallium nitride (GaN) thin films. Gallium nitratre hydrate (Ga(NO3)3.xH2O) powder, ethanol and diethanolamine (DEA) were used as starting material, solvent, and surfactant, respectively. Different amounts of DEA, i.e., 0 ml, 0.10 ml, 0.25 ml, 0.50 ml, 0.75 ml and 1.0 ml, were added into the precursor. The effects of different amounts of DEA on GaN thin films on structural and optical properties of the deposited films were investigated. High resolution X-ray diffraction results revealed that hexagonal wurtzite structure GaN thin film with (002) preferred orientation was sythesized. The intensity of the GaN(002) diffraction peaks increases with the increase of amount of surfactant from 0 ml to 0.75 ml and degraded at 1.0 ml. Raman signal of E2 (high) GaN peaks increases and becomes stronger at 0.75 ml. Further increase in the amount of surfactant has caused the intensity of E2 (high) GaN peak decreases. The measured results shows that the amount of surfactant plays an important role in improving crystallinity of GaN thin films

Effects of Withdrawal Speed on the Synthesis of GaN Thin Films by Dip Coating Method

ln this research, hexagonal wurtzite structure gallium nitride (GaN) thin films were grown on aluminium nitride on silicon substrate [AIN/Si( I I I)] substrate by using sol-gel dip coating deposition method. The effects of the withdrawal speed on the strucutural and surface morphology of the synthesis GaN thin films were investigated. The withdrawal speeds were varied from I 0-100 mm/min. High resolution X-ray diffraction results revealed that the deposited GaN thin films exhibit hexagonal wurtzite structure. The crystallite size increases with increase in withdrawal speed of substrate. Field-emission scanning electron microscopy results show that the grains were uniformly distribute over the film. While the grain size increases with increasing withdrawal speed. The results reveal that the best withdrawal speed is 100 mm/s

On The Performance Of Normalized Gain Difference Power Allocation For Mimonoma-Based VLC

In this study, we build a 4×4 multiple-input multiple-output (MIMO) nonorthogonal multiple access (NOMA) based visible light communication (VLC) system. The main goal of this study is to utilize the power consumption among the indoor VLC system by using normalized gain difference power allocation (NGDPA) to ensure the same achievable sum rate even for users on the system borders. The proposed system is simulated to serve 2, 3, and up to 4 users. The obtained results were compared with 4×4 MIMO using orthogonal frequency division multiple access (OFDMA) without applying NGDPA. It was found that the proposed system shows an almost constant achievable sum rate for all users regardless of their current position within the system coverage area. The results show that users on the system edge can share up to 97.32% of the maximum achievable sum rate. The relation between normalized offset and sum rate gain for 2, 3, and 4 users’ scenarios is also discussed. The findings reveal that the system using NGDPA scheme can utilize more sum rate gain with increasing the number of users. Through this study, it can be deduced that the 4×4 MIMO-NOMA-VLC system with NGDPA scheme has been performance