Plasma-Enhanced Chemical Vapor Deposited SiNx and SiO_2 Passivation Effects on ZnO Heterojunction Light Emitting Diodes

摘要

ZnO heterojunction light emitting diodes (LEDs) were passivated by plasma-enhanced chemical vapor-deposited SiO_2 and SiN_x. Post-dielectric deposition annealing was critical in obtaining good LED electrical and optical characteristics. No diode characteristics or light emission were observed unless the structures were annealed at 350 ℃ after fabrication. Annealed diodes showed band-edge electroluminescence (385 nm) and a broad defect band with a peak at 930 nm at room temperature. The SiO_2 and SiN_x had very different passivation effects in terms of the electrical and electro-luminescence characteristics of the LEDs. After annealing, the SiO_2 passivated ZnO LEDs showed diode IV characteristics and emitted light. However, the annealed SiN_x-passivated ZnO LEDs showed leaky diode characteristics and no light emission. We attribute these differences to the role of hydrogen on the LEDs.