Effect of surface recombination on the transient decay of excess carriers produced by short wavelength laser pulses
1982; Elsevier BV; Volume: 25; Issue: 5 Linguagem: Inglês
10.1016/0038-1101(82)90126-5
ISSN1879-2405
AutoresMohit Tyagi, J.F. Nijs, R.J. Van Overstraeten,
Tópico(s)Thermography and Photoacoustic Techniques
ResumoAbstract Effect of surface recombination on the transient decay of excess carriers injected very near to the surface region has been analysed for a semi-infinite semiconductor sample. The one dimensional continuity equation for the excess minority carriers has been solved analytically assuming that the surface recombination is important only on the front surface from which the excess carriers are injected. The decay of total excess carrier charge as a function of time is calculated for various values of the surface recombination velocities. It is found that values of S lower than 103 cm/sec. have little effect on the decay of total excess charge and the decay is exponential. For values of S larger than 104 cm/sec. the initial decay of excess charge is much faster and is dominated by the surface recombination. However, if one waits long enough for the excess carrier to diffuse into the semiconductor the decay becomes exponential when the excess charge decays to about 5% of its initial value. This exponential decay can be used to determine the excess carrier lifetime fairly accurately. A source of error in such experiments may arise from the heating of the silicon sample by the laser pulse. This effect, however is negligible for short duration pulses of low average power.
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