Optical and structural properties of GaN materials and structures grown on Si by metalorganic chemical vapor deposition (original) (raw)
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Thin Solid Films, 2006
InGaN/GaN multiple quantum well light emitting diode structures have been grown on sapphire substrates by metalorganic chemical vapor deposition. They are investigated, in this study, by high-resolution X-ray diffraction, high-resolution transmission electron microscopy, photoluminescence, and photoluminescence excitation. HR-XRD showed multiple satellite peaks up to 10th order due to the quantum well superlattice confinement effects. These indicate the high quality of layer interface structures of this sample. Excitation power-dependent photoluminescence shows that both piezoelectric field-induced quantum-confined Stark effect and band filling effect influence the luminescent properties of this sample. Temperature-dependent photoluminescence of this sample has also been studied. The peak position of the PL exhibits a monotonic red-shift and the full width at half maximum of the PL band shows a W-shaped temperature-dependent behavior with increasing temperature. From the photoluminescence excitation results, a large energy difference, so-called Stokes shift, between the band-edge absorption and emission was observed.
Investigation of GaN layer grown on Si(1 1 1) substrate using an ultrathin AlN wetting layer
Journal of Crystal Growth, 2002
High-quality GaN epilayers were grown on Si(1 1 1) substrate by metalorganic chemical vapor deposition. The growth process was featured by using an ultrathin AlN wetting layer (WL) in combination with a low-temperature (LT) GaN nucleation layer (NL). The full-width at half-maximum (FWHM) of the X-ray rocking curve for the GaN (0 0 0 2) diffraction was 15 arcmin. The dislocation density estimated from TEM investigation was found to be of the order of 10 9 cm À2 . The FWHM of the dominant band edge emission peak of the GaN was measured to be 47 meV by photoluminescence measurement at room temperature. The ultrathin AlN WL was produced by nitridation of the aluminium pre-covered substrate surface. The reflection high-energy electron diffraction showed that the AlN WL was wurtzite and the surface morphology was like the nitridated surface of sapphire by the atomic force microscopy measurement. X-ray photoelectron spectroscopy measurement showed that Si and Si x N y at a certain concentration were intermixed in the AlN WL. This study suggests that by employing an appropriate WL combined with a LT NL, high-quality heteroepitaxy is achievable even with large mismatch. r
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.
Journal of Crystal Growth, 2011
We report on the growth of thick GaN epilayers on 4-in. Si(1 1 1) substrates by metalorganic chemical vapor deposition. Using intercalated AlN layers that contribute to counterbalance the tensile strain induced by the thermal mismatch between gallium nitride and the silicon substrate, up to 6.7 mm thick crack-free group III-nitride layers have been grown. Root mean-squares surface roughness of 0.5 nm, threading dislocation densities of 1.1 Â 10 9 cm À 2 , as well as X-ray diffraction (XRD) full widths at halfmaximum (FWHM) of 406 arcsec for the GaN(0 0 2) and of 1148 arcsec for the GaN(3 0 2) reflection have been measured. The donor bound exciton has a low-temperature photoluminescence line width of 12 meV. The correlation between the threading dislocation density and XRD FWHM, as well as the correlation between the wafer curvature and the GaN in-plane stress is discussed. An increase of the tensile stress is observed upon n-type doping of GaN by silicon.
Investigation of structural, optical and morphological properties of InGaN/GaN structure
Applied Physics A, 2018
In this study, InGaN/GaN structure is investigated in the temperature range of 300-500 °C with steps of 50 °C. InGaN/ GaN multi-quantum well structure is deposited on c-orientated sapphire wafer by metal organic chemical vapour deposition method. All the parameters except for temperature kept constant during growth period. InGaN/GaN structures with different In content are investigated by XRD technique. Their structural, optical and morphological characteristics are determined by high resolution X-ray diffraction, Fourier transform spectroscopy (FTIR), photo luminescence (PL), transmission and atomic force microscopy (AFM). According to FTIR and PL spectra's, it is noticed that band gap values coincide with blue region in the electromagnetic spectrum. As a result of transmission measurements it is seen that light is completely absorbed by the sample at approximately 390 nm. Using XRD technique, dislocation densities and strain are calculated. Full width at half maximum of the XRD peak values gained from X-ray diffraction are used in an alternative method called Williamson-Hall (W-H). Using W-H method, lateral and vertical crystal lengths and tilt angles are determined. Surface roughness parameters are investigated by AFM. Different properties of GaN and InGaN layers are compared as dependent on increasing temperature. According to AFM images it is seen that these structures have high surface roughness and large crystal size. All the results yielded from the mentioned methods are in good agreement with the previous works done by different authors.
Structural and optical properties of InGaN/GaN layers close to the critical layer thickness
Applied Physics Letters, 2002
Structural and optical properties of InGaN / GaN multiple quantum wells ͑MQWs͒ grown on nano-air-bridged GaN template by metal organic chemical vapor deposition were investigated. The InGaN / GaN MQWs on nano-air-bridged GaN demonstrate much better surface morphology, revealing low defect density ϳ4 ϫ 10 8 cm −2 with step flow features measured by atomic force microscopy. The photoluminescence measurement shows one magnitude higher in intensity from less defective InGaN MQWs compared to that of the control InGaN MQWs. The improvement in photoluminescence of the InGaN MQWs is benefited from the reduction of threading dislocation density in the InGaN / GaN active layers and GaN template, revealed from cross-sectional transmission electron microscopy. High resolution x-ray diffraction analysis results show higher indium mole fraction in the MQWs when grown on nano-air-bridged GaN template, due to the strain relaxation in the nano-air-bridged GaN template. This higher indium incorporation is consistent with the redshift of the photoluminescence peak.
Influence of high-temperature AIN buffer thickness on the properties of GaN grown on Si(1 1 1)
Journal of Crystal Growth, 2003
The influences of AlN buffer thickness on the optical and the crystalline properties of metalorganic chemical vapor deposition wurtzite GaN layers on Si(1 1 1) substrate have been investigated. High-resolution X-ray diffraction and photoluminescence measurement reveal that the thickness of AlN buffer exerts a strong influence on the distribution of dislocation and stress in GaN epilayer. The evidence is further reinforced by atomic force microscopic observation of AlN nucleation process. The optimum thickness of AlN buffer to effectively suppress Si diffusion has been determined by secondary-ion mass spectroscopy to be in the range of 13-20 nm. In addition, it is found that appropriate Si diffusion in AlN buffer helps to compensate the tensile strain in GaN, which subsequently improves the optical quality of GaN on Si(1 1 1), and reduces the cracks over the GaN surface.
Thin Solid Films, 2006
A series of GaN thin films were grown on Si substrate under different conditions using metalorganic chemical vapor deposition (MOCVD) and characterized by Nomarski microscopy (NM), optical reflectance (OR), high-resolution X-ray diffraction (HRXRD), Raman scattering (RS) and photoluminescence (PL). NM showed different patterns for GaN/Si grown under different growth and source flow parameters. XRD, RS and PL measurements confirmed their wurtzite crystalline GaN structures, and the corresponding line shape analyses revealed their difference corresponding to the NM observations. The control and improvement of the crystalline cracking in GaN/Si are discussed.