Blue emission in porous silicon: Oxygen-related photoluminescence

A blue-photoluminescence (PL) band, centered at 2.6 eV, was observed in thermally and chemically oxidized light-emitting porous silicon layers with an efficiency that can exceed 0.1%. The PL decay is found to be independent of excitation intensity and detection wavelength, and to be nonexponential with a characteristic time of ∼1 nsec. A correlation between the intensity of the blue PL and the intensity of the infrared absorption related to bonded oxygen has been established. These results are examined in relation to the possible mechanisms for the blue-PL band.