SPACE-CHARGE-LIMITED CURRENTS IN TETRACENE SINGLE-CRYSTALS

It is established that gold and palladium form ohmic contacts for hole injection into sublimation grown tetracene crystals. Ohmic electron injecting contacts are formed by sodium and barium. The resulting SCL-currents can be described conventionally assuming an exponential trap distribution. Since the total trap density H0 = 3.1015cm-3 and the distribution parameter l = (Tc/T) = 4.0±0.3 turn out to be equal for electron and hole traps, we conclude that the same defects are able to trap both electron and holes. Temperature variation of the SCL-currents yields the energetic distance of the Quasi-Fermi-level of electrons respectively holes from the lowest conduction respectively valence band. Its dependence on the applied voltage is in accordance with theory. The dependence of the SCL-currents on voltage and spacing of the electrodes can be described by j ∼ (Fl+1/dl). © 1969.