Unified Model for Laser Doping of Silicon from Precursors

Laser doping of silicon with the help of precursors is well established in photovoltaics. Upon illumination with the constant or pulsed laser beam, the silicon melts and doping atoms from the doping precursor diffuse into the melted silicon. With the proper laser parameters, after resolidification, the silicon is doped without any lattice defects. Depending on laser energy and on the kind of precursor, the precursor either melts or evaporates during the laser process. For high enough laser energies, even parts of the silicon’s surface evaporate. Here, we present a unified model and simulation program, which considers all these cases. We exemplify our model with experiments and simulations of laser doping from a boron oxide precursor layer. In contrast to previous models, we are able to predict not only the width and depth of the patterns on the deformed silicon surface but also the doping profiles over a wide range of laser energies. In addition, we also show that the diffusion of the boron atoms in the molten Si is boosted by a thermally induced convection in the silicon melt: the Gaussian intensity distribution of the laser beam increases the temperature-gradient-induced surface tension gradient, causing the molten Si to circulate by Marangoni convection. Laser pulse energy densities above H > 2.8 J/cm2 lead not only to evaporation of the precursor, but also to a partial evaporation of the molten silicon. Without considering the evaporation of Si, it is not possible to correctly predict the doping profiles for high laser energies. About 50% of the evaporated materials recondense and resolidify on the wafer surface. The recondensed material from each laser pulse forms a dopant source for the subsequent laser pulses.

Correction: Analysis of ion doping profiles in Yb-doped fiber preforms using laser-induced breakdown spectroscopy

Correction for ‘Analysis of ion doping profiles in Yb-doped fiber preforms using laser-induced breakdown spectroscopy’ by Jiaming Li et al., J. Anal. At. Spectrom., 2016, 31, 492–496, DOI: 10.1039/C5JA00429B.

Компенсация нелинейности сток-затворной вольт-амперной характеристики в полевых транзисторах с длиной затвора ~100 нм

The nonlinearity of the gate–drain current–voltage characteristics in classical Schottky transistors and two-dimensional electron gas field-effect transistors based on AlGaAs/InGaAs/GaAs and InGaAs/GaAs compounds is analyzed. The carrier velocity-overshoot effect in the transistor channel is analyzed for various doping profiles of the structures under study.

Modeling and analysis of the impact of texturing angles on doping profiles in ion implanted N-type solar cells

"The aim of this paper is to develop an accurate model to study the impact of texturing angles on doping profiles in ion implanted solar cells. This study will help designers and manufacturers choose an optimal angle in texturing the surfaces of innovative solar cells. Using an optimal texturing angle will improve the performance of solar cells. Randomly chosen texturing angles may decrease the absorption of the sun light or introduce excessive defects as clustering or channeling. These defects will represent recombination centers for active electrons and holes. This will contribute seriously to the loss of the active carriers and then to the loss of solar cell efficiency. This loss is known as a recombination loss. This loss alone may reduce the efficiency of a solar cell by 20%. Numerical results showing the effects of texturing angles on doping profiles will be presented, analyzed, and validated."