Intensity of exciton luminescence in silicon in a weak magnetic field

The effect of a weak magnetic field on the intensity of photoluminescence (PL) due to exciton recombination in silicon is investigated. A considerable decrease (as much as 1040 % for a rather low optical excitation level, <1 W/cm2) in the PL intensity with above-band-gap excitation is observed with increasing magnetic field (<0.25 T). The magnitude of this change depends on optical pumping level, excitation photon energy, orientation of the crystal with respect to the magnetic field, as well as the near-surface quality of the crystal. The mechanism responsible for this phenomenon is discussed and is attributed mainly to a strong enhancement of surface recombination due to magnetic-field-induced confinement of photoexcited free carriers near the surface.