Real-time assessment of overlayer removal on GaN, AlN, and AlGaN surfaces using spectroscopic ellipsometry

Edwards, N. V.; Bremser, M. D.; Weeks, T. W.; Kern, R. S.; Davis, R. F.; Aspnes, D. E.

doi:10.1063/1.116881

Cited by 62 publications

(22 citation statements)

References 1 publication

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“…Prior to all studies the sample surface was treated as described in Ref. [13] in order to remove organic contamination and to reduce the thickness of oxide layers.…”

Section: Methodsmentioning

confidence: 99%

Dielectric function and critical points of the band structure for AlGaN alloys

Buchheim

Goldhahn

Rakel³

et al. 2005

Physica Status Solidi (b)

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The ordinary complex dielectric function (DF) of Al x Ga 1-x N alloys with 0 ≤ x ≤ 0.53 is determined by fitting spectroscopic ellipsometry data from the infrared to the vacuum ultraviolet spectral region (0.74 eV ≤ E ≤ 9.8 eV). The dispersion of the real part of the DF below the band gap is found to be in excellent agreement with previously published data. The obtained band gap energies are verified by photoluminescence and photoreflectance spectroscopy. In the high-energy range, three critical points of the band structure are clearly resolved. By applying a third-derivative based DF line shape analysis, the corresponding transition energies are determined. Their compositional dependences can be described on the basis of small bowing parameters.

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“…Prior to all studies the sample surface was treated as described in Ref. [13] in order to remove organic contamination and to reduce the thickness of oxide layers.…”

Section: Methodsmentioning

confidence: 99%

Dielectric function and critical points of the band structure for AlGaN alloys

Buchheim

Goldhahn

Rakel³

et al. 2005

Physica Status Solidi (b)

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“…[3] for bulk AlN and of Refs. [6][7] for thin films, given by the symbols. The refractive index for the AlN film #2 is 3% lower (not shown).…”

Section: Discussion Of Optical Constantsmentioning

confidence: 99%

Dielectric Function of AlN Grown on Si (111) by MBE

et al. 1999

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We measured the ellipsometric response from 0.7-5.4 eV of c-axis oriented AlN on Si (111) grown by molecular beam epitaxy. We determine the film thicknesses and find that for our AlN the refractive index is about 5-10% lower than in bulk AlN single crystals. Most likely, this discrepancy is due to a low film density (compared to bulk AlN), based on measurements using Rutherford backscattering. The films were also characterized using atomic force microscopy and x-ray diffraction to study the growth morphology. We find that AlN can be grown on Si (111) without buffer layers resulting in truely two-dimensional growth, low surface roughness, and relatively narrow x-ray peak widths.

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“…The mechanism of wet etching of GaN was illustrated to be the formation of an insoluble coating of presumably gallium hydroxide (Ga(OH) 3 ) and the subsequent dissolving in different solvents 14,16,18,23 . Many methods are used to characterize the etched surface, including scanning electron microscopic (SEM) [12][13][14][16][17][18][19][20][21]23,26,27,[29][30][31] , atomic force microscopy (AFM) 8,24,27 , transmission electron microscopy (TEM) 19,21,22 , x-ray photoelectron spectroscopy (XPS) 28 , Auger electron spectroscopy (AES) 23 , energy-dispersive x-ray analysis (EDX) 18 , x-ray diffraction (XRD) 18 , and spectroscopic ellipsometry (SE) 15 . A comprehensive review for wet chemical etching of GaN, AlN, and SiC has been presented by D. Zhuang and J. H. Edgar 5 .…”

Section: Introductionmentioning

confidence: 99%

“…Low-damaged dry etching techniques, such as ICP have been developed for device fabrication. In addition to these dry etching methods, wet chemical etching processes have been proved to be effective techniques to avoid damages introduced in etching courses [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] . In order to achieve a suitable etch rate and smooth surface, photoelectrochemical (PEC) wet etching of GaN-based materials 14,[16][17][18][19]21,[23][24][25][26][27]29,30 , which was first demonstrated by Minsky et al 14 , has been studied extensively, especially by the groups of E. L. Hu and I. Adesida 14,16,17,19,21,25,29,30 .…”

Section: Introductionmentioning

confidence: 99%

Wet chemical etching of Al 0.65 Ga 0.35 N in aqueous KOH solutions

Chen

et al. 2009

SPIE Proceedings

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We have investigated wet chemical etching of Al 0.65 Ga 0.35 N in 20% (by weight) aqueous KOH solutions at 85, 95 and 102 °C. The etch rates were 0.48, 0.64 and 0.96 μm/min, respectively. Scanning electron microscope, atomic force microscopy, Auger electron spectroscopy and x-ray photoelectron spectroscopy were employed to characterize the surface morphology and stoichiometry before and after wet chemical etching. Experimental results show that aqueous KOH solutions can effectively etch Al 0.65 Ga 0.35 N. SEM results show that the root-mean-square (rms) roughness increased from 16.189 to 50.496 nm. Degradation in surface smoothness is attributed to selective anisotropic wet chemical etching. The AES measurements show that after the untreated sample was wet chemical treated in a 20% KOH solution at 85 °C for 15 seconds, the oxide formed in the surface was removed and a lower content of oxide layer near the surface was formed and the N content is higher. XPS measurements show that the banding energies of Ga 3d shifted to low energy direction after the untreated sample was successively wet chemical treated. It indicated that the atom Ga tended to form Ga-N rather than Ga-O bonding on the surface after KOH solution treatment. The damage and oxide layer induced by dry etching processes was effectively removed by wet chemical treatment and the damage surface was refreshed.

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Real-time assessment of overlayer removal on GaN, AlN, and AlGaN surfaces using spectroscopic ellipsometry

Abstract: Spectroscopic ellipsometry was used to assess the preparation of smooth and abrupt GaN, AlN, and AlGaN surfaces by wet chemical treatments in real time. About 20–50 Å of overlayer typically can be removed from air-exposed samples.

Cited by 62 publications

References 1 publication

Dielectric function and critical points of the band structure for AlGaN alloys

Dielectric function and critical points of the band structure for AlGaN alloys

Dielectric Function of AlN Grown on Si (111) by MBE

Wet chemical etching of Al 0.65 Ga 0.35 N in aqueous KOH solutions

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