Optical properties of Ga-doped AlN nanowires

Vermeersch, Rémy; Jacopin, Gwenolé; Robin, Éric; Pernot, Julien; Gayral, B.; Daudin, B.

doi:10.1063/5.0137424

Cited by 5 publications

(6 citation statements)

References 23 publications

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“…We note that the N-rich conditions used here likely favor the formation of Al vacancies [80][81][82][83] and that O is a common background impurity in self-assembled GaN NWs grown by MBE [84]. No intense transitions are seen around 5 eV as sometimes reported for AlN NWs grown on GaN stems [36,85]. The band-edge is 75-105 meV wide, which is narrower than for AlN NWs grown on GaN stems [36,85] but broader than for direct MBE growth of AlN NWs on Si substrates (20-50 meV) [69,71], and than for vapor phase epitaxy of strain-free AlN layers (≈1 meV) [71]).…”

Section: Point Defect Incorporationsupporting

confidence: 63%

“…No intense transitions are seen around 5 eV as sometimes reported for AlN NWs grown on GaN stems [36,85]. The band-edge is 75-105 meV wide, which is narrower than for AlN NWs grown on GaN stems [36,85] but broader than for direct MBE growth of AlN NWs on Si substrates (20-50 meV) [69,71], and than for vapor phase epitaxy of strain-free AlN layers (≈1 meV) [71]). We associate the broad transition in our AlN NWs to the presence of a large density of ionized donors [86].…”

Section: Point Defect Incorporationmentioning

confidence: 58%

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Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires

John,

Gómez Ruiz,

van Deurzen

et al. 2023

Nanotechnology

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We study the molecular beam epitaxy of AlN nanowires between 950 and 1215 °C, well above the usual growth temperatures, to identify optimal growth conditions. The nanowires are grown by self-assembly on TiN(111) films sputtered onto Al2O3. Above 1100 °C, the TiN film is seen to undergo grain growth and its surface exhibits {111} facets where AlN nucleation preferentially occurs. Modeling of the nanowire elongation rate measured at different temperatures shows that the Al adatom diffusion length maximizes at 1150 °C, which appears to be the optimum growth temperature. However, analysis of the nanowire luminescence shows a steep increase in the deep-level signal already above 1050 °C, associated with O incorporation from the Al2O3 substrate. Comparison with AlN nanowires grown on Si, MgO and SiC substrates suggests that heavy doping of Si and O by interdiffusion from the TiN/substrate interface increases the nanowire internal quantum efficiency, presumably due to the formation of a SiNx or AlOx passivation shell. The outdiffusion of Si and O would also cause the formation of the inversion domains observed in the nanowires. It follows that for optoelectronic and piezoelectric applications, optimal AlN nanowire ensembles should be prepared at 1150 °C on TiN/SiC substrates and will require an ex situ surface passivation.

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Section: Point Defect Incorporationsupporting

confidence: 63%

Section: Point Defect Incorporationmentioning

confidence: 58%

Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires

John,

Gómez Ruiz,

van Deurzen

et al. 2023

Nanotechnology

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“…Accordingly, the emission lines observed below 240 nm (which corresponds to 1 ML) are assigned to the recombination of confined carriers in these incomplete QWs, with a lateral size smaller or comparable to the 2.8 nm GaN Bohr exciton radius. Emission lines above 240 nm are attributed to larger 3D GaN clusters which have also been observed [21]. They are however out of the scope of this study.…”

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confidence: 54%

Ultrathin GaN quantum wells in AlN nanowires for UV-C emission

Vermeersch¹,

Jacopin

Castioni

et al. 2023

Nanotechnology

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Molecular beam epitaxy growth and optical properties of GaN quantum disks in AlN nanowires were investigated, with the purpose of controlling the emission wavelength of AlN nanowire-based light emitting diodes. Besides GaN quantum disks with a thickness ranging from 1 to 4 monolayers, a special attention was paid to incomplete GaN disks exhibiting lateral confinement. Their emission consists of sharp lines which extend down to 215 nm, in the vicinity of AlN band edge. The room temperature cathodoluminescence intensity of an ensemble of GaN quantum disks embedded in AlN nanowires is about 20 % of the low temperature value, emphasizing the potential of ultrathin/incomplete GaN quantum disks for deep UV emission.

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“…The heterostructure consists of a 500 nm long highly conductive n-GaN stem, followed by a 150 nm n-type AlN section, a 30 nm Ga-doped AlN active area, a 150 nm long p-type AlN section, and a 15 nm p-type GaN cap, measured based on secondary electron contrast from the image acquired by scanning electron microscopy (SEM). The AlGaN active area section was grown with an extremely low Ga content of at most 1%, as measured by energy-dispersive X-ray spectroscopy (EDX) . This value, however, does not correspond to the Ga composition of the AlGaN clusters but to an averaged value over the NW diameter.…”

Section: Introductionmentioning

confidence: 99%

“…These optical properties are in line with Ga-rich AlGaN clusters resulting from Ga doping of AlN NWs. A detailed study of such features has been carried out and can be found in ref . The presence of an additional peak only at low temperature centered at around 325 nm is assigned to larger AlGaN clusters.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Electro-Optical Investigation of a Ga-Doped AlN Nanowire LED for Applications in the UV-C Range

Vermeersch

Robin

Jacopin

et al. 2023

ACS Appl. Nano Mater.

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With the aim of targeting sanitization applications, the realization of a 285 nm AlN nanowire-based light-emitting diode is reported, with a focus on the comprehensive study of its electro-optical properties. The active region consists of AlGaN, with a Ga content of at most 1%, as measured by energy-dispersive X-ray spectroscopy. Optical properties were investigated by means of cathodo-(CL) and photoluminescence. They reveal a high degree of localization of electron−hole pairs on recombination centers behaving as quantum dots. The AlN pn-junctions show diode-like rectifying behavior with 5 orders of magnitude difference between ±10 V. The main factor limiting the current at larger forward bias is found to be tunnellimited injection obeying a Fowler−Nordheim model. Spatially resolved CL and electron beam−induced current measurements demonstrate that the active region overlaps the space charge region. Finally, electroluminescence (EL) spectroscopy was performed. This methodology allowed us to identify current limitations, the main one being injection efficiency, opening the path to efficiency improvement solutions.

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Optical properties of Ga-doped AlN nanowires

Cited by 5 publications

References 23 publications

Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires

Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires

Ultrathin GaN quantum wells in AlN nanowires for UV-C emission

Comprehensive Electro-Optical Investigation of a Ga-Doped AlN Nanowire LED for Applications in the UV-C Range

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