Post-implantation depth profiling using time-domain Brillouin scattering

Abstract

The unique capabilities of time domain Brillouin scattering (TDBS) for studying post-implantation effects on optical and opto-elastic properties of semiconductors are discussed. This method utilizes coherent acoustic phonons to measure depth-dependent optical and opto-elastic changes arising from structural damage caused by ion implantation. This non-destructive technique is shown to be two orders of magnitude more sensitive than Rutherford backscattering spectrometry. Results are presented for silicon carbide (SiC), gallium arsenide (GaAs) and diamond. Using the TDBS approach, we have obtained depth-dependent profiles of the complex refractive index in hydrogen implanted 4H-SiC, and of the photoelastic coefficient in hydrogen implanted GaAs. In helium implanted diamond samples, both the complex refractive index and the photoelastic coefficient have been determined. A comparison between indirect (4H-SiC, diamond) and direct (GaAs) band gap semiconductors shows the sensitivity of TDBS to the particular optical properties of different semiconductors. These studies provide basic insight into the dependence of optical properties on defect densities created by ion implantation, which is of relevance to the fabrication of photonic and optoelectronic devices. Further development of TDBS shows promise for measuring the depth dependent positions of specific defects (color centers) in wide band gap semiconductors.