Electroluminescence with high and stable quantum efficiency and low threshold voltage from anodically oxidized thin porous silicon diode

Highly efficient electroluminescence (EL) is obtained at low operating voltage (<5 V) from $n^{+}$ -type silicon-electrochemically oxidized thin porous silicon–indium–tin–oxide junctions. Continuous wave external quantum efficiency greater than 1% and power efficiency of 0.37% have been achieved. Considerable reduction of leakage current accounts for the enhancement of EL efficiency upon oxidation. The EL time response (≈30 μs) is slower than the photoluminescence one, due to slow electrical charging of porous silicon. No degradation of quantum efficiency is observed during operation and upon aging. This is attributed to the electrochemically grown oxide, which should provide a better surface passivation than the initial hydrogen coverage.