TWO KINDS OF ELECTROLUMINESCENCE FROM POROUSSILICON IN ELECTROLYTE SOLUTIONS

Two kinds of different electroluminescence from the porous silicon grown on p-type silicon wafers were observed by applying a forward bias to porous silicon in acidic aqueous system containing strong oxidizing agents (such as 1mol·L-1HCl, 1mol·L-1 SnCl4, and 1mol·L-1 H2SO4+0.1mol·L-1 Na2S2O8). One was the red emission with low applied voltage (V+≈1.4V). Its red peak shifted to shorter wavelength as the operation time increases. It is most possibly related to the quantum size effect. The other was the white emission exhibited after the red one was quenched and when high voltage was applied on (V+>30V). It is resulted from the hot electron injection under high electric field to the thin and continuos SiO2 sub-layer formed in the porous silicon after the red emission was quenched in the electrolyte.