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Light-emitting diodes (LEDs) based on ZnO were fabricated on a p -Si substrate by using a pulsed laser deposition system. Significant electroluminescence (EL) improvement was demonstrated with the insertion of an HfO 2 electron blocking layer (EBL) in n -ZnO/ p -Si heterojunctions. Distinct near-band-edge emission at around 392 nm accompanying by a broadly strong visible emission was achieved when a proper thickness of HfO 2 EBL was used. Current-voltage and capacitance-voltage measurements confirmed that a proper thickness of the HfO 2 EBL can effectively balance the injection of electrons and holes, resulting in an increase of radiative recombination in the ZnO active layer and thus enhancing the EL performance of the devices. Five independent emissions corresponding to five different transition processes were proposed to clarify the EL origination of the n -ZnO/HfO 2 / p -Si heterojunction LEDs by Gaussian deconvolutions. It is hoped that results in this work should be helpful for the development of ZnO-based LEDs that can integrate ZnO with the Si planar technology. [ABSTRACT FROM AUTHOR]