Strong visible photoluminescence from Ge/porous Si structure

Strong visible photoluminescence was observed on Ge/porous silicon structure prepared by pulsed laser deposition of Ge on porous Si. The photoluminescence spectrum shows three subbands peaked at 400, 620, and 720 nm, respectively. The 400 nm peak was ascribed to GeO color centers, and the 720 nm peak to porous Si. The 620 nm peak is much stronger than the light emitting from the host porous Si. Photoluminescence and transmission electronic microscopy analyses suggest that the strong 620 nm luminescence is the result of the joint function of Ge and porous Si in the transition layer of Ge/porous Si structure. Plausible mechanisms for the 620 nm photoluminescence are discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)01025-0].