Browsing by Subject "B1. Silicon substrates"

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Open Access
The effect of Si(x)N(y) interlayer on the quality of GaN epitaxial layers grown on Si(111) substrates by MOCVD
(ELSEVIER, 2008-04-27) Arslan, E.; Ozturk, M. K.; Ozcelik, S.; Özbay, Ekmel
In the present paper, the effects of nitridation on the quality of GaN epitaxial films grown on Si(111) substrates by metal-organic chemical vapor phase deposition (MOCVD) are discussed. A series of GaN layers were grown on Si(111) under various conditions and characterized by Nomarski microscopy (NM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), and room temperature (RT) photoluminescence (PL) measurements. Firstly, we optimized LT-AlN/HT-AlN/Si(111) templates and graded AlGaN intermediate layers thicknesses. In order to prevent stress relaxation, step-graded AlGaN layers were introduced along with a crack-free GaN layer of thickness exceeding 2.2 mu m. Secondly, the effect of in situ substrate nitridation and the insertion of an Si(x)N(y) intermediate layer on the GaN crystalline quality was investigated. Our measurements show that the nitridation position greatly influences the surface morphology and PL and XRD spectra of GaN grown atop the Si(x)N(y) layer. The X-ray diffraction and PL measurements results confirmed that the single-crystalline wurtzite GaN was successfully grown in samples A (without Si(x)N(y) layer) and B (with Si(x)N(y) layer on Si(111)). The resulting GaN film surfaces were flat, mirror-like, and crack-free. The full-width-at-half maximum (FWHM) of the X-ray rocking curve for (0002) diffraction from the GaN epilayer of the sample B in omega-scan was 492 arcsec. The PL spectrum at room temperature showed that the GaN epilayer had a light emission at a wavelength of 365 nm with a FWHM of 6.6 nm (33.2 meV). In sample B, the insertion of a Si(x)N(y) intermediate layer significantly improved the optical and structural properties. In sample C (with Si(x)N(y) layer on Al(0.11)Ga(0.89)N interlayer). The in situ depositing of the, however, we did not obtain any improvements in the optical or structural properties.
Open Access
The electrical, optical, and structural properties of GaN epitaxial layers grown on Si(111) substrate with SiNx interlayers
(ELSEVIER, 2009-10-12) Arslan, E.; Duygulu, Ö.; Kaya, A. A.; Teke, A.; Özçelik, S.; Özbay, Ekmel
The effect of the in situ substrate nitridation time on the electrical, structural and optical properties of GaN films grown on Si(111) substrates by metal organic chemical vapor deposition (MOCVD) was investigated. A thin buffer layer of silicon nitride (SiNx) with various thicknesses was achieved through the nitridation of the substrate at different nitridation times ranging from 0 to 660 s. The surface roughness of the GaN film, which was grown on the Si substrate 10 s, exhibited a root mean square (RMS) value of 1.12 nm for the surface roughness. However, further increments in the nitridation times in turn cause increments in the surface roughness in the GaN layers. The number of threading dislocation (TD) was counted from plan-view TEM (Transmission Electron Microscopy) images. The determined density of these threading dislocations was of the order of 9×109 cm-2. The sheet resistances of the GaN layers were measured. The average sheet resistance significantly increases from 2867 Ω sq-1 for sample A (without nitridation) to 8124 Ω sq-1 for sample F (with 660 s nitridation). The photoluminescence (PL) measurements of the samples nitridated at various nitridation times were done at a temperature range of 10-300 K. A strong band edge PL emission line, which was centered at approx. 3.453 eV along with its phonon replicas which was separated by approx. 92 meV in successive orders, was observed at 10 K. The full width at half maximum (FWHM) of this peak is approx. 14 meV, which indicates the reasonable optical quality of the GaN epilayers grown on Si substrate. At room temperature, the peak position and FWHM of this emission became 3.396 eV and 58 meV, respectively.