Enhanced optical and structural properties of MBE-grown AlGaN nanowires on Si substrate by H-ion implantation and UV ozone treatment

In this work, we have proposed two ex-situ treatments to annihilate bulk defects and non-radiative surface states in MBE grown AlGaN nanowires on silicon substrate. Vertically aligned nanowires were grown by molecular beam epitaxy (Veeco Gen II) system, equipped with RF plasma source for incorporating nitrogen, at a substrate temperature of 8000C. The nanowires were structurally characterized by SEM images and an areal density of 3.8×109 nanowires-cm-2 was calculated. The peak emission wavelength was measured to be 343nm at 19K from photoluminescence (PL) measurements. The as-grown nanowires were implanted with H- ions at various energies and fluences. A 2-fold increase in PL intensity without any wavelength shift was found in sample with irradiated energy of 3 MeV and a fluency of 1×1012 ions-cm-2. X-Ray diffraction measurements on (002) diffraction peak give an FWHM of 1440 arc-sec for ionimplanted samples as compared to 1872 arc-sec for as-grown nanowires indicating an improvement in crystalline quality. The nanowires were further treated in UV ozone environment for 25 minutes and an increase of 1.6 times in PL intensity was found without any wavelength shift. Both recipes were combined to get an effective increase of 3 times in PL intensity indicating the annihilation of bulk defects and non-radiative surface states. Hence, these treatments can be used to reduce non-radiative states and can be used to increase in radiative efficiency of AlGaN nanowires for applications in UV LEDs.

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