Enhanced absorbance of a strained nanoscale Si-layered system

Abstract

Si modifications implemented at the nanoscale lead to optoelectronic and photovoltaic effects that can widen applications of conventional Si devices. The investigation exploits charge carrier and photon flux transformations at a so-called carrier collection limit. Comparison of the collection efficiencies of the same sample with and without a buried nanosystem allows a better understanding of the optical (absorbance) and electronic (carrier collection) behaviors. Experimental evidence for enhanced absorbance of a strained nanoscale Si-layered system has been found.

Non-linear optical functions of crystalline-Si resulting from nanoscale layered systems

“…Fig. 2 shows a comparison of MIND absorption coefficients obtained by PDS and of intrinsic crystalline Si [1]. Over the whole range of indirect bandgap transitions, the absorption coefficients of the strained nanoscale Si-layered system obtained by PDS are much larger (one and a half orders of magnitude) than those of the intrinsic Si (it is also greater than that of the most heavily P-doped Si shown in [6]).…”

“…3). 1 The CE is defined as the mean number of collected carriers per given wavelength photon. 4 shows the differential absorptance of a surface dead zone as a function of its thickness, for different wavelengths.…”

“…The intersection point of two curves for 1.5 eV (small diamonds from [6] and large diamonds from [1]) gives the value of the free carrier density in the MIND structure under the probing laser flux of PDS equipment. P-doping by implantation followed by a pulsed-laser annealing allows maximal/total P solubility in c-Si (ionization rate).…”

“…Optical functions of nanoscale Si-layered systems show a specific behaviour, for example, large absorption coefficients [1], and reflectivity nonlinearities [2]. The MIND (MultiInterface Novel Device [3]), that contains a heavily doped surface zone, will show there effects when exposed to a relatively important illumination.…”

Ultra-short laser ablation of dielectrics: Theoretical analysis of threshold damage fluence and ablation depth

“…The physical parameters used in these simulations are listed in Table 1. In order to compare with the experimental E p 0.033 eV The rate of electron-phonon energy transfer to the lattice [24] g 10 13 -10 15 s À1 Band gap energy [1] U I 9 e V Electron mass [27] m e 9.11 Â 10 À31 kg Electron charge [27] e 1.60 Â 10 À19 C Vacuum permittivity [27] e 0 8.9 Â 10 À12 C 2 /N m 2 Reduced Planck constant [27] £ 1.055 Â 10 À34 J s Scale constant of impact ionization [1] x 1.5 Â 10 15 Cross section for 4-photon absorption [24] s 4 2 Â 10 À114 cm 8 s 3 Reflectivity [25] R 0.927 Absorption coefficient (l = 800 nm) [26] a 1.25 Â 10 5 cm À1 Optical penetration depth d 8 Â 10 À8 m results in Refs. [1] and [21], the multiphoton ionization rates for lasers of wavelength 800 and 1053 nm are computed using the Keldysh's formula in Ref.…”