Structures and optical properties of &$text{H}_{2}^{+}$ ;-implanted GaN epi-layers

E-ISSN： 1361-6463|48|22|225101-225112

ISSN： 0022-3727

Source： Journal of Physics D: Applied Physics, Vol.48, Iss.22, 2015-06, pp. : 225101-225112

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Abstract

The implantation damage build-up and optical properties of GaN epitaxial films under &$text{H}_{2}^{+}$ ; ion implantation have been investigated by a combination of Rutherford backscattering in channeling geometry, Raman spectroscopy, UV–visible spectroscopy and transmission electron microscopy. GaN epitaxial films were implanted with 134 keV &$text{H}_{2}^{+}$ ; ions to doses ranging from 3.75 × 10¹⁶ to 1.75 × 10¹⁷ &$text{H}_{2}^{+}$ ; cm⁻² at room temperature or the same dose of 1.5 × 10¹⁷ &$text{H}_{2}^{+}$ ; cm⁻² at room temperature, 573 and 723 K. The dependence of lattice disorder induced by &$text{H}_{2}^{+}$ ;-implantation on the ion dose can be divided into a three-step damage process. A strong influence of the H concentration on the defect accumulation is discussed. The decrease in relative Ga disorder induced by &$text{H}_{2}^{+}$ ;-implantation is linear with increasing implantation temperature. The absorption coefficient of GaN epitaxial films increases with increasing ion dose, leading to the decrease in Raman scattering spectra of Ga–N vibration. With increasing implantation doses up to 5 × 10¹⁶ &$text{H}_{2}^{+}$ ; cm⁻², nanoscale hydrogen bubbles are observed in the H deposition peak region. Interstitial-type dislocation loops are observed in the damaged layer located near the damage peak region, and the geometry of the dislocation loops produced by H implantation is analyzed. The surface layer is almost free of lattice disorder induced by &$text{H}_{2}^{+}$ ;-implantation.