Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al2O3 by plasma-assisted molecular beam epitaxy

Sobanska, M.; Kłosek, K.; Borysiuk, J.; Kret, S.; Tchutchulasvili, Giorgi; Gierałtowska, S.; Żytkiewicz, Z. R.

doi:10.1063/1.4863456

Cited by 28 publications

(37 citation statements)

References 19 publications

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“…Although a large number of processes occur during sputtering, it is well established that bomb- arding a surface with energetic particles leads to the formation of surface defects, which here serve as preferential nucleation sites [18,19]. In fact, the role of surface defects as nucleation sites in catalyst-free NW growth is already established: it was found that defects ease the formation of critical nuclei and enhance the nucleation rate [20,21]. The different InAs crystal density on the two types of sputtered silicon surfaces shown in figures 2(b) and (c) is likely due to the different sputtering parameters (V sputter and t sputter ) and techniques employed.…”

Section: Methodsmentioning

confidence: 99%

Heterogeneous nucleation of catalyst-free InAs nanowires on silicon

Gomes¹,

Ercolani²,

Zannier³

et al. 2017

Nanotechnology

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Abstract. We report on the heterogeneous nucleation of catalyst-free InAs nanowires on Si (111) substrates by chemical beam epitaxy. We show that nanowire nucleation is enhanced by sputtering the silicon substrate with energetic particles. We argue that particle bombardment introduces lattice defects on the silicon surface that serve as preferential nucleation sites. The formation of these nucleation sites can be controlled by the sputtering parameters, allowing the control of nanowire density in a wide range. Nanowire nucleation is accompanied by unwanted parasitic islands, but by careful choice of annealing and growth temperature allows to strongly reduce the relative density of these islands and to realize samples with high nanowire yield.

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Section: Methodsmentioning

confidence: 99%

Heterogeneous nucleation of catalyst-free InAs nanowires on silicon

Gomes¹,

Ercolani²,

Zannier³

et al. 2017

Nanotechnology

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“…In contrast to epitaxial layers, single-crystal GaN can be grown on Si substrates as well as on amorphous substrates in the form of nanowires with diameters ranging typically between 30 and 100 nm. [1][2][3] The high crystal quality of GaN nanowires facilitates the investigation of fundamental aspects of these nanostructures by purely optical means, such as the role of the surface on their spontaneous emission. [4][5][6][7][8][9][10] These studies have shown that the nanowire surface may affect both the radiative and nonradiative recombination processes of excitons.…”

Section: Introductionmentioning

confidence: 99%

Sub-meV linewidth in GaN nanowire ensembles: Absence of surface excitons due to the field ionization of donors

et al. 2014

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We observe unusually narrow donor-bound exciton transitions (400 µeV) in the photoluminescence spectra of GaN nanowire ensembles grown on Si(111) substrates at very high (>850 ∘C) temperatures. The spectra of these samples reveal a prominent transition of excitons bound to neutral Si impurities which is not observed for samples grown under standard conditions. Motivated by these experimental results, we investigate theoretically the impact of surface-induced internal electric fields on the binding energy of donors by a combined Monte Carlo and envelope function approach. We obtain the ranges of doping and diameter for which the potential is well described using the Poisson equation, where one assumes a spatially homogeneous distribution of dopants. Our calculations also show that surface donors in nanowires with a diameter smaller than 100 nm are ionized when the surface electric field is larger than about 10 kV/cm, corresponding to a doping level higher than 2×1016cm−3. This result explains the experimental observation: since the (D+,X) complex is not stable in GaN, surface-donor-bound excitons do not contribute to the photoluminescence spectra of GaN nanowires above a certain doping level, and the linewidth reflects the actual structural perfection of the nanowire ensemble

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“…Recently, there is an increasing interest in the application of amorphous AlO y films deposited by ALD as nucleation layers for the PAMBE growth of GaN nanostructures. Such buffers effectively induce selective area formation of GaN NWs on sapphire [33] and GaN [69,70]. As shown in previous studies [34,41,71,72], AlO y buffer layers significantly enhance the nucleation rate of GaN with respect to nitridated Si without a loss of structural and optical quality [34].…”

Section: Resultsmentioning

confidence: 56%

“…Our studies show that the uniformity of the polarity of GaN NWs on Si(111) strongly depends on the procedure used for the substrate processing prior to NW growth. Interestingly, no mixed polarity was found for GaN NWs grown under similar conditions on Si(111) substrates covered by a thin amorphous AlO y buffer layer [33,34]. This shows the crucial role the chemistry at the GaN/Si(111) interface plays for the determination of GaN NWs polarity.…”

Section: Introductionmentioning

confidence: 89%

Influence of Si Substrate Preparation Procedure on Polarity of Self-Assembled GaN Nanowires on Si(111): Kelvin Probe Force Microscopy Studies

et al. 2020

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The growth of GaN nanowires having a polar, wurtzite structure on nonpolar Si substrates raises the issue of GaN nanowire polarity. Depending on the growth procedure, coexistence of nanowires with different polarities inside one ensemble has been reported. Since polarity affects the optical and electronic properties of nanowires, reliable methods for its control are needed. In this work, we use Kelvin probe force microscopy to assess the polarity of GaN nanowires grown by plasma-assisted Molecular Beam Epitaxy on Si(111) substrates. We show that uniformity of the polarity of GaN nanowires critically depends on substrate processing prior to the growth. Nearly 18% of nanowires with reversed polarity (i.e., Ga-polar) were found on the HF-etched substrates with hydrogen surface passivation. Alternative Si substrate treatment steps (RCA etching, Ga-triggered deoxidation) were tested. However, the best results, i.e., purely N-polar ensemble of nanowires, were obtained on Si wafers thermally deoxidized in the growth chamber at ~1000 °C. Interestingly, no mixed polarity was found for GaN nanowires grown under similar conditions on Si(111) substrates with a thin AlOy buffer layer. Our results show that reversal of nanowires’ polarity can be prevented by growing them on a chemically uniform substrate surface, in our case on clean, in situ formed SiNx or ex situ deposited AlOy buffers.

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Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al2O3 by plasma-assisted molecular beam epitaxy

Cited by 28 publications

References 19 publications

Heterogeneous nucleation of catalyst-free InAs nanowires on silicon

Heterogeneous nucleation of catalyst-free InAs nanowires on silicon

Sub-meV linewidth in GaN nanowire ensembles: Absence of surface excitons due to the field ionization of donors

Influence of Si Substrate Preparation Procedure on Polarity of Self-Assembled GaN Nanowires on Si(111): Kelvin Probe Force Microscopy Studies

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