We grow green light emitting diodes (LEDs) on Si(111) substrates with p-AlGaN electron blocking layers (EBLs) which have different Al frations. The results show that the variation of quantum efficiency with current density displays a diversity. At lower current densities,the quantum efficiency of LED increases with Al fraction decreasing, at higher current densities, however, the quantum efficiency of LED increases with Al fraction decreasing, which is attributed to the complicated mechnism when electron and hole are recombined in the quantum well.