A route for the top-down fabrication of ordered ultrathin GaN nanowires

Oliva, Miriam; Kaganer, Vladimir M.; Pudelski, Maximilian; Meister, Sebastian; Tahraoui, A.; Geelhaar, Lutz; Brandt, O.; Auzelle, Thomas

doi:10.1088/1361-6528/acb949

Cited by 3 publications

(3 citation statements)

References 85 publications

(122 reference statements)

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“…The HCl treatment is also seen to break most of the nanowires. As discussed in [85], the capillary forces acting at the nanowire tips when drying the sample in air are strong enough to induce buckling and breaking. Most of the measured nanowires after HCl etching are thus lying on the substrate, which enhances the coupling with laser light but may also add an inhomogeneous strain when cooling the substrate down to cryogenic temperature for PL measurements [86].…”

Section: Nanowire Luminescencementioning

confidence: 99%

Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)

et al. 2023

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The self-assembly of heteroepitaxial GaN nanowires using either molecular beam epitaxy (MBE) or metal-organic vapor phase epitaxy (MOVPE) mostly results in wafer-scale ensembles with ultrahigh (>10 μm-2) or ultralow (<1 μm-2) densities, respectively. A simple means to tune the density of well-developed nanowire ensembles between these two extremes is generally lacking. Here, we examine the self-assembly of SiNx patches on TiN(111) substrates which are eventually acting as seeds for the growth of GaN nanowires. We first found that if prepared by reactive sputtering, the TiN surface is characterized by {100} facets for which the GaN incubation time is extremely long. Fast GaN nucleation is only obtained after deposition of a sub-monolayer of SiNx atoms prior to the GaN growth. By varying the amount of pre-deposited SiNx, the GaN nanowire density could be tuned by three orders of magnitude with excellent uniformity over the entire wafer, bridging the density regimes conventionally attainable by direct self-assembly with MBE or MOVPE. The analysis of the nanowire morphology agrees with a nucleation of the GaN nanowires on nanometric SiNx patches. The photoluminescence analysis of single freestanding GaN nanowires reveals a band edge luminescence dominated by excitonic transitions that are broad and blue shifted compared to bulk GaN, an effect that is related to the small nanowire diameter and to the presence of a thick native oxide. The approach developed here can be principally used for tuning the density of most III-V semiconductors nucleus grown on inert surfaces like 2D materials.

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Section: Nanowire Luminescencementioning

confidence: 99%

Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)

et al. 2023

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“…Etching of the top c-plane in Ga-polar GaN using KOH is expected, as previously reported. 45,46 Thus, a shortening of the NW length is expected after wet etching, as depicted in Figure 3e. We measured the SiO 2 etching rate during the dry etching to be about 2 nm/min, which means that approximately 300 nm SiO 2 remained after step IV.…”

Section: Resultsmentioning

confidence: 85%

High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

da Silva,

Biegański,

Durand

et al. 2023

ACS Appl. Nano Mater.

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Ultraviolet GaN photodetectors based on nanowires (NWs) fabricated by top-down strategies promise improved uniformity, morphology, and doping control with respect to bottom-up ones. However, exploiting the advantages of the NW geometry requires sub-wavelength NW diameters. We present fabrication of large-area sub-200 nm diameter top-down GaN p–i–n NW ultraviolet photodetectors with lengths over 2 μm produced from a planar specimen using nanosphere lithography, followed by a combination of dry and crystallographic-selective wet etching. Photocurrent measurements in single-NW devices under bias show a linear response as a function of the optical power, with increased current levels under reverse bias. The linearity proves that the drift of photogenerated carriers at the junction is the dominating photodetection mechanism, with negligible contributions from surface effects. These results demonstrate that the unique properties of NW-based photodetectors can be assessed through a scalable and low-cost fabrication process.

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“…In the next step, the sample is annealed and the Pt film breaks up into an ensemble of nanoislands. These islands serve as a mask for the nanopatterning of the GaN following previously reported etching steps [21,22]. First, the buffer layer that is not protected by the nanoislands is removed by reactive ion etching (RIE).…”

Section: Methodsmentioning

confidence: 99%

Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles

Kang,

Jose,

Oliva

et al. 2024

Nanotechnology

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The dewetting of thin Pt films on different surfaces is investigated as a means to provide the patterning for the top-down fabrication of GaN nanowire ensembles. The transformation from a thin film to an ensemble of nanoislands upon annealing proceeds in good agreement with the void growth model. With increasing annealing duration, the size and shape uniformity of the nanoislands improves. This improvement speeds up for higher annealing temperature. After an optimum annealing duration, the size uniformity deteriorates due to the coalescence of neighboring islands. By changing the Pt film thickness, the nanoisland diameter and density can be quantitatively controlled in a way predicted by a simple thermodynamic model. We demonstrate the uniformity of the nanoisland ensembles for an area larger than 1 cm2. GaN nanowires are fabricated by a sequence of dry and wet etching steps, and these nanowires inherit the diameters and density of the Pt nanoisland ensemble used as a mask. Our study achieves advancements in size uniformity and range of obtainable diameters compared to previous works. This simple, economical, and scalable approach to the top-down fabrication of nanowires is useful for applications requiring large and uniform nanowire ensembles with controllable dimensions.

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A route for the top-down fabrication of ordered ultrathin GaN nanowires

Cited by 3 publications

References 85 publications

Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)

Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)

High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles

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A route for the top-down fabrication of ordered ultrathin GaN nanowires

Cited by 3 publications

References 85 publications

Density control of GaN nanowires at the wafer scale using self-assembled SiN x patches on sputtered TiN(111)

Density control of GaN nanowires at the wafer scale using self-assembled SiN x patches on sputtered TiN(111)

High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles

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Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)

Density control of GaN nanowires at the wafer scale using self-assembled SiN_x patches on sputtered TiN(111)