Raman LO phonon signal and two dimensional AFM studies on GaAs implanted by Mn ions and impact of irradiation with 5 MeV Si++ ions on it

Abstract

In the present work, gallium arsenide samples implanted with 325 keV Mn+ ions for the fluence of 5 × 1015, 1 × 1016 and 2 × 1016 ions cm−2, have been investigated using Raman scattering and Atomic force microscopy measurements. The sample implanted with the fluence of 1 × 1016 ions cm−2 was further irradiated using 5 MeV Si++ ion beams for the fluence of 1 × 1016 ions cm−2 at a substrate temperature of 350°C for recrystallization. Raman peaks obtained at 293.51 and 269.35 cm−1 were assigned to longitudinal optical (LO) phonon mode and transverse optical (TO) phonon mode of gallium arsenide, respectively. The shift in the Raman peaks towards higher wave-number with respect to ion fluence indicated the presence of residual compressive stress within the samples. The Mn and (MnAs) like mode were observed after implantation. The additional mode like GaMn was also seen in sample after irradiation with 5 MeV Si++ ions. The composition of manganese atoms in gallium arsenide estimated from the Raman spectra for the ion fluence 5 × 1015, 1 × 1016 and 2 × 1016 ions cm−2 were found to be 0.74%, 1.40% and 2.80%, respectively. The Phonon coherence length estimated from the Phonon Confinement Model by fitting the LO phonon signal was found to increase from 39.40 to 47.10 nm with respect to ion fluence. AFM images of non-implanted sample showed the smooth micrograph with root mean square surface roughness of 0.41 nm. After implantation, the different sizes of clusters were observed on the surfaces of GaAs. The shape and size of the clusters were found to depend on the ion fluence.