Forward-bias electroluminescence in ZnSe diodes

MIS devices are prepared by depositing gold, silver, or platinum contacts on thin interfacial layers of ZnO grown chemically on ZnSe substrates. The resultant diodes exhibit forward-bias electroluminescence in a band in the yellow-orange at 580 nm when the applied voltage exceeds 1.08 V. The maximum brightnesses measured were 16 ft la at 293 K and 50 ft la at 77 K for an excitation current density of 200 mA mm−2, corresponding to quantum efficiencies in excess of 10−5. A model of the potential energy diagram of the MIS structure is proposed, and is used to discuss the mode of replenishment of holes to the valence band of the ZnSe during electroluminescence emission. Hole tunnelling through the interfacial layer is thought to be unlikely, but a two-step process in which holes are excited over the hole barrier between the metal and the oxide may occur. Such a process would account for the low quantum efficiency of electroluminescence emission.