INFLUENCE OF DIFFERENT METALLIC CONTACTS ON POROUS SILICON ELECTROLUMINESCENCE

We will present data about current-induced light emission from a solid state contact between porous silicon and a metal. The contact metal c onsists of a mixture of gold and a second metal, which are coevaporate d onto the porous substrate. The quantum efficiency and the spectrum o f the fabricated device strongly depend on the second metal used for d eposition. The highest quantum efficiency is achieved by adding indium to the gold. The spectral peak positions are at 455 nm, 520 nm, 555 n m and 700 nm for indium, gallium, tin and antimony, respectively. The sample with pure gold emits at 530 nm. The electroluminescence is obse rved after first applying high reverse voltage and then switching into a.c. operation. A discussion on the origin of light emission is given in terms of defect centre luminescence in the oxide.