Assessment of Conditions Influencing Porous

Visible electroluminescence (EL) characteristics of porous Si formed on p, n, pt-n, and n-p junction substrates are studied under pulse current regime. We provide experimental proof that porous Si structures characterized by highest EL intensity have simultaneously highest photoluminescence (PL) intensity and lowest surface roughness. PL and EL can be correlated via surface roughness. Two types of EL instabilities are observed: fast, with time constant in the milliseconds range and slow, with time constant in the hours range. The fast EL instability is affected by the type of ambient and/or sample temperature during electrical excitation and is likely to be associated with the charging of the porous network. The observation of strong room temperature photolumi-nescence (PL) in porous Si1 has generated immense inter-est in the development of porous Si based light emitting devices. A major obstacle to this development being the high resistivity (>10 p-cm) of porous Si.2 It is extremely difficult to obtain efficient carrier injection in this mater-ial and therefore, electroluminescence (EL) efficiency of a solid-state porous Si diode is reportedly very low (.10-6 t