The degree of crystallinity was assessed by means of UV and visible Raman scattering measurements of Ti-implanted Si layers with very high doses (1015 to 5 x 1016/cm2) subsequently annealed by nanosecond pulsed laser melting. Ultra-heavily doped Si layers with Ti concentrations six orders of magnitude above the solid solubility limit in a layer several tens of nanometers thick were obtained. The pulsed laser melting annealing processes were needed to recover the crystal quality and to keep the high Ti concentration required to form an intermediate band. The UV Raman analysis permitted the evaluation of the lattice crystallinity of the different implanted doses probing only the implanted region and points out Ti interstitial location in the host lattice in agreement with theoretical predictions for intermediate band formation. By contrast, visible Raman spectra were only sensitive to the presence of a fully amorphized implanted layer as in the rest of the crystalline layers the probing depth far exceeds the implanted layer thickness and the signal was dominated by the undamaged Si.

UV and Visible Raman Scattering of Ultraheavily Ti Implanted Si Layers for Intermediate Band Formation. D.Pastor, J.Olea, A.del Prado, E.García-Hemme, I.Mártil, G.González-Díaz, J.Ibáñez, R.Cuscó, L.Artús: Semiconductor Science and Technology, 2011, 26[11], 115003