Determination of the optical bandgap and disorder energies of thin amorphous SiC and AlN films produced by radio frequency magnetron sputtering

Guerra, Jorge Andrés; Montañez, L; Erlenbach, Oliver; Galvez, G.; Zela, F. De; Winnacker, A.; Weingärtner, Roland

doi:10.1088/1742-6596/274/1/012113

Cited by 9 publications

(9 citation statements)

References 12 publications

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“…The obtained absorption was modeled using a sigmoidal approximation that allows the bandgap energy estimation as the intersection of the linear fitting to α 2 (E) with the X-axis. Figure 3 shows the above described fitting for the optimized sample, which leads to a bandgap estimation of 6.0 eV, in good agreement with the obtained one in sputtered AlN samples [9]. …”

Section: Effect Of Substrate Temperaturesupporting

confidence: 82%

Influence of substrate biasing on the growth of c‐axis oriented AlN thin films by RF reactive sputtering in pure nitrogen

Monteagudo-Lerma

Naranjo

González‐Herráez

et al. 2012

Phys. Status Solidi C

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We report on the investigation of the influence of deposition conditions on structural, morphological and optical properties of AlN thin films deposited on sapphire (Al 2 O 3 ) substrates by radio-frequency (RF) reactive sputtering. The deposition parameters studied are RF power, substrate temperature and substrate bias, while using pure nitrogen as reactive gas. The effect of such deposition parameters on AlN film properties are analyzed by different characterization methods as high resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy (FESEM) and linear optical transmission. AlN thin films with a full-width at half-maximum (FWHM) of the rocking curve obtained for the (0002) diffraction peak of 1.2º are achieved under optimized conditions. The time resolved evolution of the self and externally-induced biasing of the substrate during deposition process is monitored and analyzed in terms of the rate of atomic species incorporation into the layer. The bias-induced change of the atomic incorporation leads to an enhancement in the structural quality of the layer and an increase of the deposition rate.

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Section: Effect Of Substrate Temperaturesupporting

confidence: 82%

Influence of substrate biasing on the growth of c‐axis oriented AlN thin films by RF reactive sputtering in pure nitrogen

Monteagudo-Lerma

Naranjo

González‐Herráez

et al. 2012

Phys. Status Solidi C

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“…In Fig. 3 we compare our data with data from the literature selected as mentioned above; data include Fagen [14], Matsunami et al [15], Dutta et al [16], Heckens and Woollam [17], Sundaram et al [18], and Guerra et al [19]; most data include only k. There is a large dispersion of k data. Only the Heckens k data match the present one; the match of the Heckens data in n is not as good as in k, but the differences are not very large.…”

Section: Resultsmentioning

confidence: 99%

Self-consistent optical constants of SiC thin films

et al. 2011

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The optical constants of ion-beam-sputtered SiC films have been measured by ellipsometry in the 190 to 950 nm range. The set of data has been extended both toward shorter and longer wavelengths with data in the literature, along with inter- and extrapolations, in order to obtain a self-consistent set of data by means of Kramers-Krönig analysis. All data correspond to films that were deposited by sputtering on nonheated substrates, and hence they are expected to be amorphous. A bandgap of 1.9 eV for the films was fitted from the obtained optical constants. A good global accuracy of the data was estimated through the use of various sum rules. The consistent dataset includes the visible to the extreme ultraviolet (EUV); this large spectrum of characterization will enable the design of multilayer coatings that combine a high reflectance in parts of the EUV with desired performance at a secondary range, such as the visible. To our knowledge, this paper provides the first compilation of the optical constants of amorphous SiC films.

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“…In the case of amorphous AlN, such Urbach tails may lead to absorption coefficients exceeding 100 cm -1 for energies above 4 eV [56]. Urbach tails also exist in single crystals with high structural or vibrational disorder, e.g.…”

Section: Optical Absorptionmentioning

confidence: 99%

Growth of AlN bulk crystals on SiC seeds: Chemical analysis and crystal properties

Bickermann

Filip²,

Epelbaum³

et al. 2012

Journal of Crystal Growth

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Highlights:-Different growth conditions used to control SiC incorporation in AlN bulk growth -Phonon energies and band-gap of the crystals close to 'pure AlN' -Deep-UV opacity regardless of silicon and carbon content -Two types of samples with very different absorption and luminescence -No pseudo-binary alloy, but highly compensated, Si/C co-doped AlN Abstract AlN single crystals are grown by physical vapor transport (PVT) in sintered TaC crucibles in the presence of SiC, i.e. by seeding on 6H-SiC or by adding SiC to the AlN source material. Different growth conditions, i.e. growth temperatures T = 1900-2050°C and off-orientation angles in respect to [0001]  = 0-42°, are applied in order to investigate to which extent the incorporation of Si and/or C can be controlled during PVT growth. Chemical analysis is performed by energy-dispersive X-ray analysis (EDX), secondary ion mass spectrometry (SIMS), and Rutherford backscattering spectroscopy (RBS). The grown crystals are significantly contaminated with Si and C in the range of several atomic percents, but they do not represent pseudo-binary AlN-SiC solid solutions. Samples cut from these crystals are probed by Raman micro-spectroscopy, optical absorption, cathodoluminescence (CL), and near band-gap photoluminescence (PL) in order to evaluate the crystal properties. All crystals exhibit phonon bands at the positions of AlN phonon energies, and a low-temperature band-gap exceeding 5.8 eV, which is only slightly lower than the band-gap of pure AlN. On the other hand, the samples show very different optical properties below the band-gap, including coloration. As the changes in optical properties do not correlate to chemical analysis, we suggest that self-compensation of silicon 2 and carbon as well as formation of intrinsic defects lead to a complex compensation scenario in the samples. The grown crystals are thus to be considered as highly compensated, Si/C co-doped AlN.

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Determination of the optical bandgap and disorder energies of thin amorphous SiC and AlN films produced by radio frequency magnetron sputtering

Cited by 9 publications

References 12 publications

Influence of substrate biasing on the growth of c‐axis oriented AlN thin films by RF reactive sputtering in pure nitrogen

Influence of substrate biasing on the growth of c‐axis oriented AlN thin films by RF reactive sputtering in pure nitrogen

Self-consistent optical constants of SiC thin films

Growth of AlN bulk crystals on SiC seeds: Chemical analysis and crystal properties

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