L. Shekari

Optical and Structural Characterizations of GaN Nanostructures

In this paper, we have grown high-quality wurtzite GaN nanowires (NWs) on polished <111> silicon (Si) either with or without gold (Au) as catalyst, by thermal evaporation using commercial GaN powder in an atmosphere of argon (Ar) gas. Optical and structural characterizations were performed using photoluminescence (PL), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and high resolution X-ray diffraction (HR-XRD). Structural characterizations indicate that the nanowires are of single-crystal hexagonal GaN. By using catalyst the growth location and diameters of the NWs can be controlled. The NWs on the Si are of higher density, and the compositional quality of the grown NWs on the Si substrate is of pure GaN as compare to the Au-coated substrate.

Synthesis of GaN Nanoparticles by DC Plasma Enhanced Chemical Vapor Deposition

The unique optical properties of nanostructured GaN basically, turn it as a very important part of many electronic and optoelectronic devices such as high power transistors, UV detectors, solar cells, lasers and blue LED. The aim of the current study is GaN nanoparticle deposition at low temperature in preferred direction. In this work, GaN nanoparticles were prepared using direct current plasma enhanced chemical vapor deposition (DC-PECVD) method on Si (100) wafer as a substrate at 700°C. Gallium metal and nitrogen plasma were used as precursors. GaN nanoparticles were grown based on the direct reaction between gallium atoms and excited nitrogen species in the plasma. Structural and morphological characterizations of GaN nanoparticles were carried out using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field emissions electron microscopy (FE-SEM). Preferred (100) direction of GaN nanostructures which obtained by careful control of processing parameters, were revealed by XRD. FE-SEM images show the average diameter of nanoparticles is 37 nm. The EDS results show the Ga to N ratio in the sample was 8.8 to 1.2 by weight which is very close to the Ga to N ratio of prefect GaN crystal. The deviance is related to the nitrogen vacancy of the sample. These results demonstrate a simple inexpensive method for GaN nanoparticle deposition at low temperature which is critical for many of applications.

Growth and characterization of high-quality GaN nanowires on PZnO and PGaN by thermal evaporation

In the current research, an easy and inexpensive method is used to synthesize highly crystalline gallium nitride (GaN) nanowires (NWs) on two different substrates [i.e., porous zinc oxide (PZnO) and porous gallium nitride (PGaN)] on Si (111) wafer by thermal evaporation without any catalyst. Microstructural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of the substrates in the nucleation and alignment of the GaN NWs. Further structural and optical characterizations were performed using high-resolution X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Results indicate that the NWs have a single-crystal hexagonal GaN structure and growth direction in the (0001) plane. The quality and density of GaN NWs grown on different substrates are highly dependent on the lattice mismatch between the NWs and their substrates. Results indicate that NWs grown on PGaN have better quality and higher density compared to NWs on PZnO.

Characterization of GaN nanowires grown on PSi, PZnO and PGaN on Si (111) substrates by thermal evaporation

In this research, we used an easy and inexpensive method to synthesize highly crystalline GaN nanowires (NWs); on different substrates such as porous silicon (PSi), porous zinc oxide (PZnO) and porous gallium nitride (PGaN) on Si (111) wafer by thermal evaporation using commercial GaN powder without any catalyst. Micro structural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of different substrates in the morphology, nucleation and alignment of the GaN nanowires. The degree of alignment of the synthesized nanowires does not depend on the lattice mismatch between wires and their substrates. Further structural and optical characterizations were performed using high resolution X-ray diffraction and energy-dispersive X-ray spectroscopy. Results indicate that the nanowires are of single-crystal hexagonal GaN. The quality and density of grown GaN nanowires for different substrates are highly dependent on the lattice mismatch between the nanowires and their substrates and also on the size of the porosity of the substrates. Nanowires grown on PGaN have the best quality and highest density as compared to nanowires on other substrates. By using three kinds of porous substrates, we are able to study the increase in the alignment and density of the nanowires.

Gan Nanowire Growth by Thermal Evaporation Method

In this research we introduce an inexpensive method to produce highly crystalline GaN Nanowires (NWs) grown on porous zinc oxide (PZnO) using commercial GaN powder, either in argon gas or combination of nitrogen and Ar gas atmosphere, by thermal evaporation. Morphological structural studies using transmission electron microscope (TEM) and scanning electron microscopy (SEM) measurements showed the role of porosity and different gas flowing, in the alignment and nucleation of these NWs. The NWs grown under flow of mix gases have very different diameters of between 50 and 200 nm, but those which were grown in Ar gas atmosphere, have rather uniform diameter of around 50 nm. The length of the GaN NWs was uniform, (around 10 µm). Optical and structural characterizations were performed by energy-dispersive X-ray spectroscopy (EDX) and high resolution X-ray diffraction (HR-XRD). Results revealed that these NWs are of single-crystal hexagonal GaN with [oooı] and [ıoīı] growth directions for the NWs grown under Ar and mixed gas flow.

Fabrication and Structural and Optical Characterizations of GaN Nano and Micro Structures Grown by Thermal Evaporation Method

Abstract. Gallium Nitride (GaN) nano and micro structures were grown on different substrates, such as ceramic boat and alumina plate using thermal evaporation method with commercial GaN powder under the flow of Argon (Ar) gas atmosphere. Micro structural studies by scanning electron microscopy (SEM) revealed the role of different substrates in the nucleation of the GaN nano and micro wires and ribbons. Additional structural and optical characterizations were performed using energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. Results indicated that the nanowires and nanoribbons are of single-crystal hexagonal GaN and are more and less orderly in their growth with different substrates. The quality of growth of the GaN nanowires and nanoribbons for different substrates is highly dependent on the lattice mismatch between the nanowires and their substrates and it also depends on the conditions of the growth.