Sub-bandgap absorption in Ti implanted Si over the Mott limit

Abstract

We have analyzed the structural and optical properties of Si implanted with very high Ti doses and subsequently pulsed-laser melted (PLM). After PLM, all samples exhibit an abrupt and roughly uniform, box-shaped Ti profile, with a concentration around 2 Â 10 20 cm À3, which is well above the Mott limit, within a 150 nm thick layer. Samples PLM-annealed at the highest energy density (1.8 J/cm 2 ) exhibit good lattice reconstruction. Independent of the annealing energy density, in all of the samples we observe strong sub-bandgap absorption, with absorption coefficient values between 4 Â 10 3 and 10 4 cm À1. These results are explained in terms of the formation of an intermediate band (IB) originated from the Ti deep levels.

Room temperature photo-response of titanium supersaturated silicon at energies over the bandgap

“…The duration of the pulse was 20 ns and only one pulse was fired at each location. With this laser process we guarantee a good crystal quality of the resulting layers [6,14,16].…”

Optical and electrical properties of textured sulfur-hyperdoped silicon: a thermal annealing study

“…Due to the multiple reflection taking place at the rough interface between the air and the textured hyperdoped layer, and at the internal interface between the textured hyperdoped layer and the Si substrate, as well as at the flat interface between the back surface of Si substrate and the air, it is very difficult to perform a optical analysis. In order to simplify this optical model, firstly we neglect the reflection at the internal interface between the hyperdoped layer and the Si substrate, which is considered to be reasonable; 25,26 secondly, the rough textured hyperdoped structure is equated to be a flat one. This treatment of equating will not affect the conclusion of optical analysis because that here we only care about the variation trend, rather than the accurate values, of the optical constants of hyperdoped samples after thermal annealing, and also because that the different annealed hyperdoped samples own the same surface morphology, sample structure and optical measurement condition.…”

Ion implantation and pulsed laser melting processing for the development of an intermediate band material

“…This valley indicates the beginning of the solidifying front, from where the superficial 40 nm has been melted while the layer beyond has been only heated but not melted. In the case of the double implanted sample the valleys do not appear and a boxshaped depth profile can be clearly observed [9,10]. This shows that a region deeper than the implanted layer has been melted.…”

“…This shows that a region deeper than the implanted layer has been melted. Crystalline recovery has been studied in similar implanted samples by means of electron diffraction, transmission electron microscopy and glancing incidence X -ray diffraction showing that after the PLM process, a high crystalline structure is obtained [10,11]. In a detailed Raman spectroscopy characterization no evidences of secondary phase formation (like Ti silicides) has been observed in samples with similar implanted doses [12].…”