Synthesis of hexagonal and cubic GaN thin film on Si (111) using a low-cost electrochemical deposition technique (original) (raw)
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Journal of Crystal Growth, 2002
The initial growth of hexagonal GaN films grown on Si(1 1 1) substrates coated with an ultra-thin SiC buffer layer was studied. It was found that a 2.5-nm-thick SiC layer is an effective buffer layer for GaN growth on an Si(1 1 1) substrate. Under Ga-rich growth conditions, Ga adatoms, in comparison to those under N-rich growth conditions, were highly mobile. Consequently, the GaN films had a flat surface and an almost stacking-fault-free microstructure. The initial GaN nucleations quickly coalesced laterally to submicron-sized grains. Under N-rich growth conditions, the initial GaN nucleations saturated at a diameter of about 50 nm (measured at the film surface). The grown GaN films showed statistical roughening of the surface and a characteristic columnar structure. The yellow-band luminescence (YL) was sensitive to the microstructures of the GaN films prepared under almost the same growth conditions, suggesting that the Ga-vacancy is not the sole source of YL.
Journal of Crystal Growth, 2011
This paper reports the synthesis and characterization of GaN thin films deposited on Si (1 1 1) substrate, using electrochemical deposition technique below room temperature for different durations. The effects of deposition duration on the morphology, structure and optical properties of GaN thin films are reported. The SEM images showed different surface morphologies of the grown structures on Si substrate for different duration times. The shape and the dimensions of the structures were also found to be dependent on the growth time. From XRD analysis the lattice constants, the average size of h-GaN crystals and the in-plane (along a-axis) and out of plane (along c-axis) strains were calculated. The effects of deposition duration on crystal parameters from XRD and Raman modes were investigated. Photoluminescence spectrum showed that the energy gaps of h-GaN and c-GaN were about 3.39 and 3.2 eV, respectively, at room temperature and the PL-intensity of h-GaN increased with deposition duration. The growth mechanism is also proposed.
Effect of thickness on the structural and optical properties of GaN films grown on Si(111)
Journal of Materials Science: Materials in Electronics, 2011
GaN films with different thicknesses were grown on Si(111) substrates by Plasma-Assisted Molecular Beam Epitaxy (PA-MBE). The optical properties of the films were investigated using spectrophotometric measurements of the reflectance in the wavelength range 200-3,300 nm. With increasing film thickness, the refractive index (n) increased slightly, while the optical energy gap (E g) changed with no specific trend. The structural properties of the grown films were studied at (002) reflections using two types of rocking curve measurements; normal rocking curve (x-scan) and triple axis rocking curve (x/2h-scan). The Full Width at Half Maximum (FWHM) of rocking curve decreased with increasing film thickness. Hall effect measurements showed that all the samples were n-type with carrier concentrations decreasing from 8.025 9 10 18 to 5.65 9 10 17 cm-3 , and mobility increasing from 14 to 110 cm 2 V-1 s-1 as increasing the film thickness from 590 to 1,420 nm, respectively. Photoluminescence (PL) spectra for the grown GaN films with different thicknesses were measured at room temperature. PL spectra for all the samples exhibited band edge (BE) emissions at peak energies of 3.24 eV, with peak intensities increased with increasing the film thickness. 2 Experimental methods GaN films were grown in Riber 32P molecular beam epitaxy (MBE) machine equipped with a 2,200 L/s turbo-molecular
The optical properties and electronic transitions of cubic (fl) and hexagonal (a) GaN films grown by electron-cyclotron resonance molecular beam epitaxy were investigated in the energy region from 1.5 to 10 eV with conventional and synchrotron radiation ellipsometry. This is the first direct observation of the dielectric function of both polytypes in this energy region. The fundamental absorption of fl-GaN is located at a lower energy than that of a-GaN. The observed structures are different for both phases and are analysed in the temperature range 80-650 K. With reference to electronic band structure calculations, the transitions are assigned to specific regions in the respective Brillouin zones. Finally, the refiectivities of a-GaN and fl-GaN are compared with contradictory results in the literature.
International Journal of Materials Science and Applications, 2013
The crystalline quality of wider direct band gap semiconductor (3.4 eV)hexagonal GaN (h-GaN)epilayer grown on Si(111)is evaluated by using different growth approaches and interlayer's. The investigations of GaN epilayer crystal quality for the template of converted porous GaN layer formed by novel nitridation process of thin (2 and 0.5µm)GaAs layer on Si(111)and on C + ion implanted very thin SiC layer formed on Si(111)and grown ambient effect are made. Epilayer grown on thinner non-isoelectronic converted SiC templates is found to broaden its PL line width whereas epilayer grown on porously converted GaN layer fromed from iso-electronic GaAs (111)layer on Si(111)is found narrow line width. H 2 ambient grown film better crystalline quality and higher PL Ex. peak energy is found as compared to N 2 ambient grown film. Low temperature PL measurement, similarity between defect related donor-acceptor peaks (DAP)to defect related yellow band luminescence at the room temperature PL measurement is also found. Grown epilayer different characterization reveals better crystalline quality h-GaN is achieved by using thin iso-electronic GaAS interlayer on Si(111)with H 2 grown ambient.
Growth of hexagonal GaN thin films on Si(1 1 1) with cubic SiC buffer layers
Journal of Crystal Growth, 1998
The growth of GaN films on silicon or sapphire substrates has not been straightforward due to their large mismatch ( '13%). SiC is structurally the closest material to GaN (especially cubic form) and has a small lattice mismatch (3.5%) between SiC and GaN, and therefore can be useful as the substrate for GaN. Single-crystal wafers of cubic SiC and GaN, however, are hard to obtain and have not been produced commercially yet. Therefore, a thin layer of cubic SiC on substrates such as Si and oxide single crystals might solve this problem and will be one of a suitable buffer layers for the cubic GaN film growth. Epitaxial cubic SiC buffer layers were grown on either carbonized or uncarbonized Si(1 1 1) substrates as low as temperature of 830°C using a supersonic molecular jet of t-butyldimethylsilane, (CH ) CSiH(CH ) , and the polycrystalline hexagonal GaN thin films were subsequently deposited on them at 600°C using a MOMBE system. The buffer layers and the GaN films were characterized by AES, XRD, FTIR, ellipsometry, and X-ray phi()-scan measurements. The growth temperature of t-butyldimethylsilane was much lower than conventional CVD growth temperatures and this is the first report to obtain epitaxial cubic SiC films on Si from t-butyldimethylsilane and new attempt to grow h-GaN thin films on cubic SiC buffer layers.
Materials Science and Engineering: B, 1995
The optical properties and electronic transitions of cubic (fl) and hexagonal (a) GaN films grown by electron-cyclotron resonance molecular beam epitaxy were investigated in the energy region from 1.5 to 10 eV with conventional and synchrotron radiation ellipsometry. This is the first direct observation of the dielectric function of both polytypes in this energy region. The fundamental absorption of fl-GaN is located at a lower energy than that of a-GaN. The observed structures are different for both phases and are analysed in the temperature range 80-650 K. With reference to electronic band structure calculations, the transitions are assigned to specific regions in the respective Brillouin zones. Finally, the refiectivities of a-GaN and fl-GaN are compared with contradictory results in the literature.
Characterization of GaN grown on patterned Si(111) substrates
Journal of Crystal Growth, 2004
GaN films were grown on patterned-Si(1 1 1) substrates by metal organic chemical vapor deposition (MOCVD). Arrays of rectangular stripes and squares, with a 3.5-mm height and different lateral dimensions were patterned and etched on Si substrates using inductively coupled plasma reactive ion etching. A low temperature 24-nm-thick AlN (grown at 720 1C) was used as the seed layer for growing GaN films of 0.3-to 2-mm thick. For ridges wider than 2 mm, crack-free flat-top GaN films were obtained with a surface roughness of $0.7 nm. Localized Raman spectroscopy was conducted to study the stress distribution in the GaN films on Si ridges and squares. Substantial stress relaxation was observed in GaN on patterned Si area. The crystalline microstructure of GaN films was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and atomic force microscopy.
High Quality GaN Layers Grown by Metalorganic Chemical Vapor Deposition on Si(111) Substrates
physica status solidi (a), 1999
GaN layers are grown onto silicon (111) substrates by metalorganic chemical vapor phase deposition (MOCVD). The X-ray and photoluminescence spectra as well as the surface morphologies of the layers are comparable to the characteristics of GaN layers grown on sapphire substrates. Linewidths of 610 arcsec in the case of the GaN(0002) reflection in the X-ray w-scan and 13 meV at 10 K for the dominant excitonic photoluminescence at 3.44 eV as well as a surface roughness below 2 nm (rms) are observed. The high quality has been achieved by a careful optimization of AlAs/AlN buffer layers on the Si substrates.