Steady-state and time-resolved photoluminescence from relaxed and strained GaN nanowires grown by catalyst-free molecular-beam epitaxy

Abstract

We report steady-state and time-resolved photoluminescence ͑TRPL͒ measurements on individual GaN nanowires ͑6-20 m in length, 30-940 nm in diameter͒ grown by a nitrogen-plasma-assisted, catalyst-free molecular-beam epitaxy on Si͑111͒ and dispersed onto fused quartz substrates. Induced tensile strain for nanowires bonded to fused silica and compressive strain for nanowires coated with atomic-layer-deposition alumina led to redshifts and blueshifts of the dominant steady-state PL emission peak, respectively. Unperturbed nanowires exhibited spectra associated with high-quality, strain-free material. The TRPL lifetimes, which were similar for both relaxed and strained nanowires of similar size, ranged from 200 ps to over 2 ns, compared well with those of low-defect bulk GaN, and depended linearly on nanowire diameter. The diameter-dependent lifetimes yielded a room-temperature surface recombination velocity S of 9 ϫ 10 3 cm/ s for our silicon-doped GaN nanowires.

Imaging transport in nanowires using near-field detection of light

“…Effective diffusion length also depends on nanowire diameter, consistent with the TRPL studies in GaN [17] and near-field scanning photocurrent measurements in very small diameter ZnO nanowires [18].…”

Facile synthesis and photoluminescence spectroscopy of 3D-triangular GaN nano prism islands

“…It is well established that the TRPL measurements on individually dispersed and as-synthesized GaN nanostructures give a PL decay time in the range of ∼200 ps to about ∼2.7 ns dependent on the temperature and the dimensions of the nanostructure. 10 Fig. S5 † represents the decay profile of samples grown at RT, 450 and 600°C.…”

“…A variety of techniques for GaN growth have been employed including the extensively used techniques such as vapour-liquid-solid (VLS), 7,8 metal-organic chemical vapour deposition (MOCVD) 9 and molecular beam epitaxy (MBE). 7,10 In the present investigation, the sputtering gun technique has been employed for GaN synthesis which is a relatively inexpensive and simpler technique that offers the possibility of growth at a lower substrate temperature. 11,12 This technique has a different growth mechanism than evaporation deposition where substances are deposited on or forced into a lattice without chemical reaction.…”

Well-arranged novel InGaN hexagonal nanoplates at the tops of nitrogen-polarity GaN nanocolumn arrays

“…Although the surface of the InGaN hexagonal nanoplates was exposed to air, visible emission was obtained, indicating a slow nonradiative surface recombination rate for the GaN-based nanocrystals. 6,21 The PL FWHM of the nanoplate sample was evaluated to be 103 nm, which is double the electroluminescence FWHM of well developed amber (594 nm) InGaN LEDs. 22 The spatial fluctuation in the In composition of InGaN increases with increased In composition; therefore, one of the reasons for the broad PL spectrum was the compositional fluctuation of In inside each nanoplate.…”