Rare earth ion Er

+

has been implanted in porous silicon at 350 keV ion energy in 1×10

12

~1×10

15

cm

2

dose range. After implantation the porous silicon still presented bright visible emission. After annealing

1.54 μm characteristic emissions of Er

3+

in PSi have been measured

and its intensity is much more intense than that of Si processed by same conditions. Further experiments show that enhancement of the Er

3+

emission relates to the surface layer of porous silicon. There are a lot of impurity in the surface layer

such as O

C

F etc. Those impurities can form a variety of complex with Er which is favourable for decreasing segregation of Er during annealing

and increasing Er concentration. It is probable that the impurities introduced by electrochemical process give'rise to 1.54 μm luminescence enhancement.