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Abstract
The effects of ex-situ annealing in a N2 ambient on the properties of GaAs/GaAsSbN/GaAs core-multi-shell nanowires on Si (111) substrate grown by self-catalyzed molecular beam epitaxy (MBE) are reported. As-grown nanowires exhibit band edge emission at ~0.99 eV with a shoulder peak at ~0.85 eV, identified to arise from band tail states. A large red shift of 7 cm−1 and broadened Raman spectra of as-grown nanowires compared to that of non-nitride nanowires confirmed phonon localization at N-induced localized defects. On annealing nanowires to 750 °C, there was no change in the planar defects in the nanowire with respect to the as-grown nanowire; however, vanishing of the photoluminescence (PL) peak corresponding to band tail states along with enhanced band edge PL intensity, recovery of the Raman shift and increase in the Schottky barrier height from 0.1 to 0.4 eV clearly point to the efficient annihilation of point defects in these GaAsSbN nanowires. A significant reduction in the temperature-induced energy shift in the annealed nanowires is attributed to annihilation of band tail states and weak temperature dependence of N-related localized states. The observation of room temperature PL signal in the 1.3 μm region shows that the strategy of adding small amounts of N to GaAsSb is a promising route to realization of efficient nanoscale light emitters with reduced temperature sensitivity in the telecommunication wavelength region.
Highlights
Dilute nitride III–V semiconductor alloys in thin films with variable bandgap have been on the extensively studied material systems [1,2,3,4,5,6,7,8,9,10] for optical telecommunications applications
We present the effects of ex-situ rapid thermal annealing (RTA) on the optical properties of GaAs/ GaAsSbN/GaAs nanowires grown by self-catalyzed molecular beam epitaxy (MBE)
With a shoulder at lower energy attributed to band tail states, 4 K μ-PL spectra of the unannealed nanowires display a peak at ~0.99 eV
Summary
Dilute nitride III–V semiconductor alloys in thin films with variable bandgap have been on the extensively studied material systems [1,2,3,4,5,6,7,8,9,10] for optical telecommunications applications. We have reported successful growth of self-catalyzed GaAs/ GaAsSbN/GaAs core-multi-shell nanowires emitting at ~1.3 μm [11]. These nanowires exhibited planar defects in addition to point defects, which is in contrast to thin films where only the latter dominates [12]. It is necessary to investigate the effect of defects and annealing on dilute nitride nanowires to understand and improve the optical properties
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