Resonant-cavity organic light-emitting diodes for low-cost optical interconnects on CMOS silicon circuits

The possibility to integrate an optical emitter at any point in a silicon integrated circuit would represent a major breakthrough in the field of optical interconnects. The outstanding properties of luminescent organic semiconductors, such as their ability to be deposited on various substrates and their efficiency, make them good candidates for this kind of applications, but organic light-emitting diodes (OLEDs) are characterized by broad spectra and angular emission patterns which prevent their integration in an optical interconnection system. So, we study resonant-cavity organic light-emitting diodes (RC-OLEDs) such as Al/ITO/CuPc/TPD/Alq3/Al which are made on silicon substrates. Aluminum is chosen to make the mirrors because of its compatibility with CMOS technology. The devices are characterized by electroluminescence, and their current-voltage characteristics are measured. We study the influence of the electrodes on the electrical characteristics of the devices. We describe these planar multilayer microcavities using a transfer-matrix multiplication method. The experimental results that we obtain with two samples allow us to calculate the dependence of the refractive index of the ITO layer on the wavelength. We compare our experimental and theoretical results and find a good agreement between them.