Indium implantation and annealing of GaN: Lattice damage and recovery

Abstract

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)

N‐ and Ga‐K‐edge XAFS study of the effect of annealing on In implanted GaN

“…Among some of the heavily implanted samples, the use of the third cumulant, c 3 , was found to be necessary in order to improve the fitting quality. The variation of the nn coordination numbers with Φ is consistent with the defect concentration determined with RBS [7]. More specifically, the defect concentration exhibits a twostep sigmoidal-like dependence on logΦ indicating the synergy of direct impact and defect accumulation mechanisms [11].…”

“…Rutherford Backscattering (RBS) characterization has shown that ion implantation results in the formation of a highly defective layer extending throughout the GaN film. At fluences higher than 1×10 -15 cm -2 an amorphous layer that extends up to 200 nm from the surface is formed [7].…”

Penetration Resistance and Penetrability in Pyramidal (Nano)Indentations

“…This can be demonstrated with n ‐type gallium nitride after its 700 keV indium implantation when a subsurface defective region was formed to a depth of 400 nm. The gradients depended on the indium fluencies and were analyzed by Rutherford backscattering and Raman spectra (Katsikini et al ., . The loading curves upon Berkovich ( R = 120 nm) indentation of Kavouras et al .…”