Indium implantation and annealing of GaN: Lattice damage and recovery

The effect of Indium (In) implantation in n-type GaN is studied using Raman spectroscopy and Rutherford backscattering (RBS). The RBS analysis reveals that the 700 keV In implantation results in the formation of a subsurface defective region that extends to a depth of 400 nm. An abrupt increase (∼93%) of the maximum defect concentration is observed for fluences in the range 1.5 and 5×1014 cm-2. A further increase of the fluence to 5×1015 cm-2 renders the implanted layer amorphous. In the Raman spectra recorded in the backscattering geometry only the E22 peak is resolved since the A1(LO) is completely damped due to plasmon - phonon coupling. As the fluence increases, the characteristic sharp peaks of the as-grown sample broaden due to relaxation of the q-selection rules allowing phonons with q ≠ 0 to contribute in the Raman scattering. Furthermore, three additional broad peaks are detected in the implanted samples even after implantation with the fluence of 5×1013 cm-2. They are ascribed to disorder activated Raman scattering or acoustic overtones (300 cm-1, 420 cm-1) and the formation of point defects (670 cm-1), respectively. Rapid thermal annealing at 1000 °C causes partial recovery of the lattice. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)