InGaN/GaN MQW blue light emitting diode(LED) structures whose p-GaN cap layers were grown with various flow rates of Cp_2Mg and p-GaN films with the same growth conditions were grown by MOCVD.The LEDs were fabricated and characterized by I-V measurement in order to investigate the effects of this varied growth condition on the electrical character of the devices.As the Cp_2Mg flow rate increased,the forward voltage of the LEDs decreased at first and then increased at a certain Cp_2Mg flow rate,and the leakage current increased without discontinuity.It was found that low Cp_2Mg flow rate can lead to low hole concentration and poor electrical property of the p-GaN cap layer,but high Cp_2Mg flow rate made the situation even worse,the surface morphology and crystallinity of the films become rough and worse.This was responsible for the changes of the electrical character of the LEDs.