Hybrid silicon-organic light emitting diodes for 1.5 μm optoelectronics

Electroluminescent diodes fabricated on silicon substrates which emit at a wavelength of 1.5 μm have been demonstrated. The diodes operate at room temperature and exhibit good I-V characteristics. The diodes use an erbium tris(8-hydroxyquinoline) (ErQ) layer as electron transporting and emitting layer and use N, N′-diphenyl-N, N′-bis(3-methyl)-1,1′-biphenyl-4,4′-diamine (TPD) as the hole transporting layer. Hole injection into the diodes is from a p⁺⁺ silicon substrate anode and aluminum is used as the cathode electrode. The devices demonstrated start to exhibit electroluminescence at a voltage of ∼17 V and the electroluminescence intensity rises sub-linearly with the current density through the device. At a drive voltage of 33V the diodes have an internal efficiency of ∼0.01%. We have measured the luminescence lifetime for the 1.5 μm emission and obtained a value of ∼200 μs. Using this value and estimating the total concentration of erbium present in the diodes we calculate a theoretical maximum optical power generation in these diodes of ∼100 mW.