Improvement of the light extraction efficiency in n-ZnO:Ga/p-Si heterojunction light emitting diodes by a SiO₂ current-blocking layer

We studied the role of a patterned SiO₂ current-blocking layer (CBL) on the output power in polycrystal n-type ZnO:Ga/p-Si heterojunction light emitting diodes (LEDs). The introduction of a CBL considerably improved the light extraction efficiency by about 200%, despite the increased series resistance. It suppressed the vertical current with a low extraction efficiency by opaque metals and allowed the spreading current component to be enhanced, in contrast to conventional n-ZnO/p-Si LEDs operated only a vertical current component due to the grain boundaries in the ZnO films. This result suggests that the use of CBL is profitable method in the emitter application using the film with the polycrystal structure.