SILICON COMPATIBLE ORGANIC LIGHT-EMITTING DIODE

As an effort toward a goal of monolithic optoelectronics for silicon (Si) chip-to-chip connections, we have fabricated organic light emitting diodes (LED's) using either heavily N-doped silicon (Si) as a cathode or P-doped Si as an anode. A thin silicon dioxide (SiO2) layer, thermally grown on Si before deposition of a polymer or a molecular organic layer, enhances the electron injection into the semiconducting emissive layer; Without the thin oxide layer, no light was observed from LED's made from either (2-methoxy, 5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene) (MEH-PPV) or 8-hydroxyquinoline aluminum (Alq), With the SiO2 layer, the internal quantum efficiencies as high as 0.02% and 0.5% have been observed for MEH-PPV and Alq, respectively, and the turn-on voltages were as low as 2.5 V and 8 V, again for MEH-PPV and Alq, respectively. From the LED response time measurement, we identified RC constant and the recombination time of transport-related traps as the speed limiting factors.