Defect engineering on demand in GaAsN nanowires by <i>post-growth</i> hydrogen irradiation

In bulk and nanostructured semiconductors, the optical properties are usually engineered by varying crystal growth conditions or by applying high strain levels. Here, we report post-growth band-structure engineering in nanowires by mere exposition to low-energy ionized hydrogen gas. Our GaAs/GaAsN core/multishell nanowires contain 0.7%, 2% and 3% N [1]. At these low concentrations (typical of dilute nitrides), N atoms behave as strongly localized and perturbing lattice defects, and give rise to a number of counterintuitive effects. Among others, we observe a giant red-shift of the GaAsN bandgap as high as 0.5 eV with increasing N from 0 to 3%. We demonstrate that these defects can be engineered on demand, as the hydrogenation allows to passivate N by forming N-H complexes and thereby tune the GaAsN bandgap up to the value of the GaAs [2]. This N passivation is accompanied by a photoluminescence signal increase of more than an order of magnitude. The approach creates new, fast and effective possibilities for tuning the optical properties of nanowires at the nanoscale and forming highly efficient site-controlled quantum dots at telecom wavelengths.

[1] M Yukimune et al 2019 Nanotech. 30 244002
[2] F Biccari et al 2018 Adv. Mater. 30, 1705450