Nanoscale Welding and Strain‐Engineered Photoluminescence of GaN Nanowires

Strain engineering is a powerful tool for the development of nanostructured semiconductor devices. In this work, the effect of high external elastic strain is investigated on the photoluminescence of GaN nanowires (NWs). Individual horizontal NWs are strained to bending strains up to 2.2% using an atomic force microscope (AFM) probe. Novel nanomanipulation techniques for mechanical fixation of strained low aspect ratio NWs transferred on the auxiliary substrate are developed, including the “nanoscale welding” based on conductive AFM. The optical properties of the strained GaN NWs are investigated using spatial mapping of the microphotoluminescence. It is shown that bending strain leads to symmetric broadening of photoluminescence peak. The obtained spectra are numerically analyzed taking into account the non‐uniform strain distribution, selection rules, and strain‐induced bandgap modification, showing that the main contribution to luminescence corresponds to transitions from the conduction band to the heavy hole band. A linear coefficient of shift (broadening) of the luminescence maximum was derived for a bending (uniaxial) deformation of 131.5–136.5 meV/GPa.