Nitride-based LEDs fabricated on ZnO-buffered sapphire substrates

In this study, we fabricated nitride-based blue light emitting diodes (LEDs) on sapphire substrates presenting ZnO buffer layers, which we prepared through metal–organic chemical vapor deposition. The introduction of the ZnO buffer layer, which acted as an additive for liquid phase sintering of the low temperature-grown GaN layers during the temperature ramping period from 550 to 1040 °C, favored subsequent two-dimensional GaN growth and decreased the threading dislocation density. The resulting nitride-based blue LEDs exhibited improved performance, characterized by a typical forward bias voltage of 3.32 V at an injection current of 20 mA and a reverse current of 2.67 × 10−8 A at a reverse bias of 10 V. The ideality factor was 2.64 at a forward bias of 2.50 V and the external quantum efficiency was 11.38% at an injection current of 20 mA.

► ZnO buffer layer was prepared through metal-organic chemical vapor deposition.
► ZnO buffer layer transport phenomenon during the temperature ramping period is proposed.
► The GaN/ZnO nucleation layer is effective at decreasing the defect formation.
► The introduction of a ZnO buffer can improve the electro-optical properties of LEDs.