Optical and structural properties of InN grown by HPCVD (original) (raw)
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Optical and structural properties of InN grown by HPCVD
Ninth International Conference on Solid State Lighting, 2009
The optical and structural properties of InN layers grown by 'High Pressure Chemical Vapor Deposition' (HPCVD) using a pulsed precursor approach have been studied. The study focuses on the effect of ammonia precursor exposure time and magnitude on the InN layer quality. The samples have been analyzed by X-ray diffraction, Raman scattering, infra red reflectance spectroscopy and photoluminescence spectroscopy. Raman measurements and X-ray diffraction showed the grown layers to be single phase InN of high crystalline quality. The E 2 (high) Raman mode showed FWHM's as small as 9.2 cm -1 . The FWHM's of the InN(0002) X-ray Bragg reflex in the 2Θ-Ω-scans were around 350 arcsec, with rocking curve values as low as 1152 arcsec Photoluminescence features have been observed down to 0.7 eV, where the low energy cutoff might be due to the detector limitation. The analysis of the IR reflectance spectra shows that the free carrier concentrations are as low as 3.3·10 18 cm -3 for InN layers grown on sapphire substrates.
Optical characterization of InN layers grown by high-pressure chemical vapor deposition
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2008
The optical properties of InN layers grown by high-pressure chemical vapor deposition have been studied. Raman, infrared reflection, and transmission spectroscopy studies have been carried out to investigate the structural and optical properties of InN films grown on sapphire and GaN/sapphire templates. Results obtained from Raman and IR reflectance measurements are used to estimate the free carrier concentrations, which were found to be varying from mid 10 18 to low 10 20 cm −3. The values for free carrier concentrations are compared to optical absorption edge estimates obtained from optical transmission spectra analysis. The analysis shows that optical absorption edge for InN shifts below 1.1 eV as the free carrier concentration decreases to low 10 18 cm −3 .
Properties of InN grown by High-Pressure CVD
MRS Proceedings, 2005
Group III-nitride compound semiconductors (e.g. AlN-GaN-InN) have generated considerable interest for use in advanced optoelectronic device structures. The fabrication of multi-tandem solar cells, high-speed optoelectronics and solid state lasers operating at higher energy wavelengths will be made possible using (Ga 1-y-x Al y In x )N heterostructures due to their robustness against radiation and the wide spectral application range. To date, the growth of indium rich (In 1x Ga x )N films and heterostructures remains a challenge, primarily due to the large thermal decomposition pressures in indium rich group III-nitride alloys at the optimum growth temperatures. In order to control the partial pressures during the growth process of InN and related alloys, a unique high-pressure chemical vapor deposition (HPCVD) system with integrated real-time optical monitoring capabilities has been developed. We report initial results on InN layers grown at temperatures as high as ~850°C with reactor pressures around 15 bar. Such process conditions are a major step towards the fabrication of indium rich group III-nitride heterostructures that are embedded in wide band gap group III-nitrides. Real-time optical characterization techniques are applied in order to study the gas phase kinetics and surface chemistry processes during the growth process. For an ammonia to TMI precursor flow ratio below 500, multiple phases with sharp XRD features are observed. Structural analysis perform by Raman scattering techniques indicates that the E 2 high mode improves as NH 3 :TMI ratio is decreased to below 500. Optical characterization of these InN layers indicates that the absorption edge shifts from down from 1.85 eV to 0.7 eV. This shift seems to be caused by a series of localized absorption centers that appear as the indium to nitrogen stoichiometry varies. This contribution will correlate the process parameters to results obtained by XRD, Raman spectroscopy and optical spectroscopy, in order to assess the InN film properties.
Applied Physics Letters, 2008
The influence of substrate polarity on the properties of InN layers grown by high-pressure chemical vapor deposition has been studied. The 2⌰-x-ray diffraction scans on InN layers deposited on polar GaN epilayers revealed single-phase InN͑0002͒ with a full width at half maximum ͑FWHM͒ of around 200 arc sec. InN layers grown on N-polar GaN exhibit larger FWHMs. Rocking curve analysis confirmed single-phase InN for both growth polarities, with FWHM values for -RC͑002͒ at 2080 arc sec for InN grown on Ga-polar templates. The A 1 ͑LO͒ Raman mode analysis shows higher free carrier concentrations in InN grown on N-polar templates, indicating that polarity affects the incorporation of impurities.
Structural and optical characterisation of InN layers grown by MOCVD
2004
In the following, we report investigations of the dependencies of the structural, optical and electrical characteristics of InN thin films grown by MOCVD on the growth temperature. The layer thicknesses range from 70 to 400 nm. Their carrier concentrations range from 7 × 10 18 to 4 × 10 19 cm −3 . Hall mobility values from 150 to 1300 cm 2 /V/s were determined in these films. The variation of the growth temperature and V/III ratio brought about different growth modes and rates. Using TEM, in addition to measuring layer thickness, we also determined the growth mode along with the structural quality of the InN layers. The surface roughness was obtained from AFM measurements. The layer crystalline quality was also investigated by means of X-ray diffraction in the rocking mode. Photoluminescence measurements performed at room temperature and at 7 K gave emission at around 0.7 eV.
Effect of V/III molar ratio on the structural and optical properties of InN epilayers grown by HPCVD
Twelfth International Conference on Solid State Lighting and Fourth International Conference on White LEDs and Solid State Lighting, 2012
The dependency of the structural and optoelectronic properties of InN thin films grown by high-pressure chemical vapor deposition technique on the group V/III molar precursor ratio has been studied. X-ray diffraction, Raman spectroscopy, and IR reflectance spectroscopy have been utilized to study local-and long-range structural ordering as well as optoelectronic properties of the InN epilayers grown on crystalline sapphire substrates. The investigated InN epilayers were grown with group V/III molar precursor ratio varying from 900 to 3600, while all other growth parameters were kept constant. For a group V/III precursor ratio of 2400, the full width-half maximum of the Raman E 2 (high) mode and XRD (0002) Bragg reflex exhibit minimums of 7.53 cm⁻¹ and 210 arcsec, respectively, with maximized grain size and reduced in-plane strain effect. FTIR data analysis reveals a growth rate of 120 nm/hr, a carrier mobility of 1020 cm²V⁻¹s⁻¹, and a free carrier concentration of 1.7×10 18 cm⁻³ for a V/III ratio of 2400. The Raman analysis indicate that non-polar E 2 (high) mode position remains unaffected from a changing V/III ratio; whereas, polar A 1 (LO) mode position significantly changes with changing V/III ratio. Optical analysis also suggests that LO-phonon correlates with free carrier concentration (n e ) and TO-phonon correlates with free carrier mobility (μ) in the InN epilayers.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016
Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein–Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates.
Depth dependence of structural quality in InN grown by metalorganic chemical vapor deposition
Materials Letters, 2007
Rutherford backscattering and channeling is combined with X-ray diffraction to study the depth dependence of crystalline quality in InN layers grown by metalorganic chemical vapor deposition on sapphire substrate. The poorest crystalline quality in InN layer is produced at the intermediate region over 100 nm away from the InN/sapphire interface. With increasing layer thickness the crystalline quality improves to a certain degree dependent on the growth temperature. The InN sample grown at 450°C is found to be more homogeneous than the sample grown at 550°C. The difference in the defect profile is explained by the temperature-dependent growth modes. The inhomogeneity of structural quality and related properties such as carrier concentration and strain field is possibly the reason to observe a high energy wing in PL spectrum of the InN sample grown at 550°C.
Optical properties of InN grown on Si(111) substrate
Physica Status Solidi A-applications and Materials Science, 2010
A comprehensive characterization of the optical properties of wurtzite InN films grown by molecular beam epitaxy on Si(111) substrates is presented. Two types of films are investigated in this work: InN on AlN/Si(111) and InN on GaN/AlN/Si(111). Their properties are compared to a layer deposited on GaN/sapphire substrate. The dielectric function (DF) is obtained from spectroscopic ellipsometry (SE). The infrared studies yield the plasma frequency and thus the electron density, while the interband absorption is probed between 0.56 and 9.8 eV. For InN grown on Si(111) substrate, the absorption onset is slightly shifted to higher energies with respect to the InN film grown on GaN/sapphire which can be attributed to higher electron concentrations. Despite this, strongly pronounced optical transitions due to critical points of the band structure are found in the high-energy part of the DF. It emphasizes the already promising quality of the InN films on silicon. Band-gap renormalization (BGR), band filling, and strain are taken into account in order to estimate the intrinsic band gap of wurtzite InN. For the InN layers on silicon, we get a band gap between 0.66 and 0.685 eV.
Depth dependence of structural quality in InN grown by MOCVD
2007
Rutherford backscattering and channeling is combined with X-ray diffraction to study the depth dependence of crystalline quality in InN layers grown by metalorganic chemical vapor deposition on sapphire substrate. The poorest crystalline quality in InN layer is produced at the intermediate region over 100 nm away from the InN/sapphire interface. With increasing layer thickness the crystalline quality improves to a certain degree dependent on the growth temperature. The InN sample grown at 450°C is found to be more homogeneous than the sample grown at 550°C. The difference in the defect profile is explained by the temperature-dependent growth modes. The inhomogeneity of structural quality and related properties such as carrier concentration and strain field is possibly the reason to observe a high energy wing in PL spectrum of the InN sample grown at 550°C.