Surface preparation of substrates from bulk GaN crystals

Hanser, Drew; Tutor, M.; Preble, E. A.; Williams, Mark; Xu, Xueping; Tsvetkov, D.; Liu, Lianghong

doi:10.1016/j.jcrysgro.2007.03.039

Cited by 77 publications

(107 citation statements)

References 15 publications

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“…two groups were respectively treated with different polishing procedures (Procedures 1 and 2). Procedure 1 was developed in house where the substrate surface was grounded and lapped with diamond media, followed by a two-step mechanical polishing to prepare the surface for the chemical mechanical polishing (CMP) [8]. Procedure 2 was carried out at Sinmat, Inc. (Gainsville, FL) with proprietary polishing process.…”

Section: Methodsmentioning

confidence: 99%

Cathodoluminescence evaluation of subsurface damage in GaN substrate after polishing

Lai

Johnson

Paskova

et al. 2009

Phys. Status Solidi (c)

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The surface of HVPE grown GaN substrates were treated with two different polishing procedures. Both procedures were successful in producing highly smooth and featureless surfaces. However, subsurface damage was observed in the sample treated by one of the procedures. The subsurface damage was revealed by cathodoluminescence (CL) spectroscopy imaging but was not visible by scanning electron microscopy (SEM) or Atomic force microscopy (AFM). Thermal annealing at 950 °C with different gases was performed in an attempt to remove subsurface damages. Annealing in gas mixtures containing H2 increased both the presence of surface scratches and overall surface roughness. On the other hand, annealing in mixtures of NH3 and N2 (with no H2) led to the surfaces with significantly reduced subsurface damage. The surface roughness and optical properties of the sample after the annealing with such gas mixtures were slightly sacrificed. In order to evaluate subsurface damage depth, CL images were taken from the annealed surface for different acceleration voltages. The results suggest that the observed subsurface damages were within 1.48 μm of the surface. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Methodsmentioning

confidence: 99%

Cathodoluminescence evaluation of subsurface damage in GaN substrate after polishing

Lai

Johnson

Paskova

et al. 2009

Phys. Status Solidi (c)

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“…The damage layer decreases by reducing the grain size of abrasives, applying lower pressure and choosing appropriate pads. Epitaxial growth studies on similarly mechanically polished samples resulted in dislocations propagating in the epitaxial layers, increased the surface roughness, and scratches highlighted in the epitaxial layer surface morphology [10]. In order to prepare AlN substrate surfaces for epitaxy, an additional CMP technique was used.…”

Section: Resultsmentioning

confidence: 99%

“…The enhancement of the contrast and sharpness of the pseudo Kikuchi pattern is due to the removal of subsurface damage and due to the improved lattice perfection. Polishing damage, which generates networks of dislocations at or near the surface region of the substrate, can be also imaged with the CL technique [10]. Figure 6 displays a monochromatic CL image of the CMP surface.…”

Section: Resultsmentioning

confidence: 99%

Surface preparation of AlN substrates

Chen

Siche

Albrecht

et al. 2008

Cryst. Res. Technol.

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The Al-polar surfaces of AlN wafers cut from physical vapor transport grown crystals were lapped and polished. Polishing procedures were developed to produce surfaces for epitaxial growth. The surface scratches and subsurface damage caused by mechanical polishing were removed by a final chemical mechanical polishing (CMP) process, which yielded a perfect surface ready for epitaxial growth. After CMP the average root mean square surface roughness on a 5 µm × 5 µm area was 0.1 nm. Characterization of the polished surfaces by electron back scatter diffraction and cathodoluminescence showed no subsurface damage. The difference of orientation dependent material removal rate during CMP went up with the increase of the misorientation from (0001) surface.

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“…1(a)]. 3 Another high-temperature reactively sputtered AlN buffer was also found to be effective in suppressing defect formation in the GaN nucleation region [48]. This buffer approach also permits reducing of tensile stress during GaN growth by forming a weak interface, which leads to optimized structural properties [48] of films with thickness up to $1-2 mm.…”

Section: A Single Substrate Developmentmentioning

confidence: 99%

GaN Substrates for III-Nitride Devices

2010

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| Despite the rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics, their full potential is limited by two primary obstacles: i) a high defect density and biaxial strain due to the heteroepitaxial growth on foreign substrates, which result in lower performance and shortened device lifetime, and ii) a strong built-in electric field due to spontaneous and piezoelectric polarization in the wurtzite structures along the well-established [0001] growth direction for nitrides. Recent advances in the research, development, and commercial production of native GaN substrates with low defect density and high structural and optical quality have opened opportunities to overcome both of these obstacles and have led to significant progress in the development of several optoelectronic and high-power devices. In this paper, the recent achievements in bulk GaN growth development using different approaches are reviewed; comparison of the bulk materials grown in different directions is made; and the current achievements in device performance utilizing native GaN substrate material are summarized.

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Surface preparation of substrates from bulk GaN crystals

Cited by 77 publications

References 15 publications

Cathodoluminescence evaluation of subsurface damage in GaN substrate after polishing

Cathodoluminescence evaluation of subsurface damage in GaN substrate after polishing

Surface preparation of AlN substrates

GaN Substrates for III-Nitride Devices

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