LUMINESCENT CHARACTERISTICS OF A NOVEL POROUS SILICON STRUCTURE FORMED IN A NONAQUEOUS ELECTROLYTE

Novel porous silicon layers which photoluminesce and electroluminesce in an aqueous solution have been formed by oxidation of (100) silicon in anhydrous acetonitrile-HF solutions. The novel porous structures co nsisted of large, noninterconnected pores, 1-2 mum diam, which grew no rmal to the surface. The pores were spaced 2-3 mum apart, and the leng th, which could be over 150 mum, was dependent on etch time and curren t density. Microporous structures (i.e., <100 nm), often associated wi th luminescence from porous silicon, were not detected by TEM, SEM, or infrared examination. The porous surface was hydride terminated, whic h was critical to the luminescence process. Since water and oxygen wer e not present during the formation of the porous structure and the por es were relatively large, neither silicon-oxygen species (e.g., siloxe nes) nor quantum size structures, appeared necessary for the generatio n visible luminescence from porous silicon.