Morphology and arrangement of InN nanocolumns deposited by radio-frequency sputtering: Effect of the buffer layer

Abstract

a b s t r a c tWe present the structural and optical properties of (0001)-oriented nanocolumnar films of InN deposited on c-sapphire substrates by radio-frequency reactive sputtering. It is observed that the column density and dimensions are highly dependent on the growth parameters of the buffer layer. We investigate four buffer layers consisting of (i) 30 nm of low-growth-rate InN, (ii) 30 nm of AlN deposited on the unbiased substrate (us), (iii) 30 nm of AlN deposited on the reverse-biased substrate (bs), and (iv) a 60-nm-thick bilayer consisting of 30-nm-thick bs-AlN deposited on top of 30-nm-thick us-AlN. Differences in the layer nucleation process due to the buffer layer induce variations of the column density in the range of (2.5-16) Â 10 9 cm À 2 , and of the column diameter in the range of 87-176 nm. Best results in terms of mosaicity are obtained using the bs-AlN buffer layer, which leads to a full width at half-maximum of the InN(0002) rocking curve of 1.2°. A residual compressive strain is still present in the nanocolumns. All samples exhibit room temperature photoluminescence emission at $ 1.6 eV, and an apparent optical band gap at $ 1.7 eV estimated from linear optical transmittance measurements.

Development of AlInN photoconductors deposited by sputtering

“…Figure shows the transmittance spectrum of the thickest layer (350 nm). The band gap energy has been estimated through a sigmoidal approximation , obtaining a value of ∼ 2.15 eV (576 nm), which is consistent with a blue‐shift of the expected band gap due to a Burstein–Moss effect, as the expected carrier concentration in the layers is in the range of 1.6 × 10 20 cm −3 . This band gap energy is in agreement with other results in AlInN layers grown by magnetron sputtering and presenting similar alloy composition .…”

Growth of Catalyst-Free Hexagonal Pyramid-Like InN Nanocolumns on Nitrided Si(111) Substrates via Radio-Frequency Metal–Organic Molecular Beam Epitaxy

“…InN nanocolumns have been grown using various methods, including radio-frequency (RF) molecular beam epitaxy (MBE) [12], RF sputtering [13], and metal-organic chemical vapor deposition (MOCVD) [14]. However, because of the low dissociation efficiency of ammonia, these methods require large amounts of ammonia to obtain the flux of active nitrogen required for producing high-quality nitride.…”

Long-range ordered vertical III-nitride nano-cylinder arrays via plasma-assisted atomic layer deposition

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Numerous types of nitride nanostructures have been explored via either templateassisted or template-free fabrication methodologies. [14][15][16][17] In the template-assisted strategy, material growth is carried out on sacrificial nanostructured template materials such as carbon nanotubes, polymers, or anodic aluminum oxide (AAO). [18][19][20] Subsequent to growth, the template material is typically removed via high-temperature treatment (calcination) or physical/chemical etching to obtain various kinds of free-standing nanostructures.…”