Carrier Injection Characteristics in Diamine/ZnSe Organic-Inorganic Thin-Film Heterostructures for Blue Electroluminescence

Blue electroluminescence, peaking at a wavelength nearly corresponding to the band gap of ZnSe, is observed in a Au/diamine(TAD)/ZnSe/GaAs/In structure, where TAD/ZnSe layers are successively grown on a GaAs substrate using molecular beam epitaxy/deposition. Investigations of carrier injection characteristics at the heterostructure revealed that (i) electrons and holes accumulate at the TAD/ZnSe interface under positive bias application to the Au electrode, (ii) a strong electric field formed by the accumulated electrons and holes, ∼107 V/cm2, lowers the potential barriers at the TAD/ZnSe interface for both electrons and holes, (iii) holes injected from TAD to ZnSe recombine with electrons, resulting in sharp blue electroluminescence in the ZnSe layer. The similarity of these processes to those at practical organic/organic interfaces suggests that these kinds of tunneling injections are commonly applicable for explanation of the operation of organic electroluminescent devices.