Giant enhancement of free charge carrier concentration in boron-doped amorphous hydrogenated silicon under femtosecond laser crystallization

Abstract

The modification of boron-doped amorphous hydrogenated silicon films [a-Si:H(B)] with femtosecond laser radiation is studied in this work. It is demonstrated that femtosecond laser crystallization of the a-Si:H(B) film area leads to extremely high values of the free charge carrier (hole) concentration, which is typical for degenerated semiconductors. The free charge carrier concentration is locally determined by measuring the Raman spectra in the modified areas. The shape of Raman spectra is typical for Fano resonance. It is found that the charge carrier concentration in the modified areas may exceed 1020 cm−3 depending on the femtosecond irradiation conditions. The areas with such a high concentration of free charge carriers are also characterized by high volume fraction of crystalline phase (more than 90%). Such a sharp increase in the free charge carrier concentration in the modified areas may be explained by an increase in concentration of electrically active boron atoms. The activation energy of the temperature dependence of the conductivity for laser beam treated areas is in full agreement with the data obtained from the analysis of the Raman scattering spectra.

Laser‐induced heating of porous Ge layers implanted with Ag+ and Cu+ ions

“…Heating and crystallization of amorphous Si and Ge layers is mostly carried out by high-power pulsed lasers, and probing carried out by continuous-wave (cw) lowpower lasers during subsequent Raman studies usually does not lead to strong heating and crystallization under the laser probe beam. [11,12] It is known that complex experiments were also carried out on the irradiation of a thin layer of amorphous Ge with a pulsed laser and the simultaneous observation of the crystallization process in a transmission electron microscope. [13] The implantation of metal ions with high doses leads to the formation of porous Ge (PGe) layers.…”

Femtosecond Laser Fabrication of Anisotropic Structures in Phosphorus- and Boron-Doped Amorphous Silicon Films

“…In the last decade, considerable interest has been shown to femtosecond laser irradiation of thin amorphous silicon (a-Si) films. Such treatment generates not only the occurrence of LIPPS [ 3 , 4 , 18 , 28 ], but also suppression of photodegradation and the rise of both optical absorption [ 30 , 31 ] and electrical conductivity in the irradiated a-Si film [ 4 , 32 ]. Therefore, the femtosecond laser processing of a-Si opens new prospects for photovoltaics.…”

“…Therefore, the femtosecond laser processing of a-Si opens new prospects for photovoltaics. Herein it is important that this technology is a complex process that affects not only the surface of the material, but also its phase composition, e.g., formation of a significant crystalline Si (c-Si) volume fraction in the a-Si film [ 28 , 32 , 33 ]. As a result, modulation of the crystalline and amorphous phases distribution can occur within the formed LIPSS [ 3 , 18 ], along with the relief modulation affect the anisotropy of the optical and electrical properties of a-Si film, which may be applicable for polarization-sensitive optics and sensors [ 18 , 28 ].…”