Eur. Phys. J. Appl. Phys.
Volume 34, Number 3, June 2006
|Page(s)||189 - 195|
|Section||Laser and Optics|
|Published online||24 June 2006|
Electrical analysis of femtosecond laser pulse absorption in silicon
Analog Devices, Raheen, Limerick, Ireland
2 National Center for Laser Applications (NCLA), National University of Ireland-Galway, Galway, Ireland
Corresponding author: email@example.com
Revised: 18 November 2005
Accepted: 6 January 2006
Published online: 24 June 2006
We report a study of femtosecond laser pulse absorption of wafer grade silicon with an average pulse duration of 150 fs, centred on a wavelength of 775 nm. The electrical response of the laser excited carriers, over a range of fluences up to the ablation threshold for silicon is analysed. The silicon used for the experiments is a uniformly doped P-type wafer with a concentration of 1 × 1012 cm−3 throughout its volume. The purpose of this work is to use the electrical properties of the excited carriers as a method for analysing the interaction between femtosecond pulses and the silicon lattice below the ablation threshold, and to determine the evolution of the excited carriers after the femtosecond pulse is absorbed in silicon. This paper uses simulation software to solve the ambipolar continuity equation for the evolution of the excited carrier group given the initial values and boundary conditions of the experimental system. The paper derives results for the total number of excited carriers created as a function of laser fluence, in addition to the bulk excited carrier dynamics and lifetime after femtosecond laser excitation. Based on the results for the total number of excited carriers as a function of the average laser fluence, a value of 0.09 J cm−2 is measured as the fluence where lattice defects started to reduce the effective quantity of carriers that could be detected and hence indicated incubation lattice damage.
PACS: 42.62.-b – Laser applications / 72.20.Jv – Charge carriers: generation, recombination, lifetime, and trapping / 78.68.+m – Optical properties of surfaces / 71.35.Ee – Electron-hole drops and electron-hole plasma
© EDP Sciences, 2006
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