Exploring ion beam techniques for III-nitride optoelectronic applications

Wide and direct band gap semiconductors, in particular group-III-nitrides, have been investigated intensively in the last two decades as materials for opto-electronic devices. InGaN quantum wells are the basis of highly efficient commercial light emitting diodes (LEDs) emitting from the near-UV to the blue spectral region. AlGaN is used for the fabrication of deep-UV LEDs as well as of high electron mobility transistors (HEMTs). However, nitride LEDs still suffer from low efficiencies for longer wavelengths, in particular in the red and green spectral region. Moreover, GaN-based nanowires (NWs) are attracting research interest as material for efficient light emitters and sensors. The incorporation of rare earth (RE) elements into nitride hosts allows the fabrication of devices operating from the ultraviolet (UV) to the infrared (IR) spectral region thanks to the narrow and temperature stable intra 4f-shell transitions of the trivalent RE ions.

Ion beam techniques appear a powerful tool for materials modification and materials characterization. In fact, ion implantation is useful technique to reproducibly incorporate dopants with controllable profiles. However, this technique creates defects degrading the optical properties of the material, therefore, defect formation and annealing processes need to be well understood. Thus in order to increase the knowledge on the created defects and to achieve optimal activation of RE ions, several ion beam techniques were explored. Rutherford backscattering spectrometry/channelling (RBS/C), heavy ion elastic recoil detection analysis (HI-ERDA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray absorption (XAS) were carried out to investigate the structural properties of the materials and the radiation defects. And finely photoluminescence spectroscopy (PL) and cathodo-luminesces were performed to have look at the optical activation.

Results shows high potential of Eu-doped Al_xGa_1-xN alloys and nitride nanostructures for the fabrication of optoelectronic devices operating at long wavelength in particular in the red spectral region.

Key words: ion implantation, AlGaN alloys, nanowires, rare earth, ion beam analysis, optical activation.