High light output efficiency of n-ZnO/p-GaN heterojunction light-emitting diodes fabricated with a MgF₂ electron-blocking layer

MgF₂ electron-blocking layers (EBLs) were used for improving the light output efficiency of n-ZnO/p-GaN heterojunction light-emitting diodes (LEDs). The turn-on voltage of the LEDs fabricated with MgF₂ EBLs was as low as 4.4V, and their optical light output power was nearly 2-fold higher than that of the reference LEDs without EBLs. This difference could be attributed to a combination of the following effects. First, interfacial damage could be suppressed by a reliable EBL formation comprising Mg-O-F structures, thus reducing the non-radiative recombination via deep trap states at the junction. Second, the electron-hole confinement at the EBL/n-ZnO interface could contribute toward enhancing the radiative recombination.