As the size of complementary metal-oxide-semiconductor(CMOS)transistors scales down,the operating frequency of integrated circuitry is increasingly limited by the long metal wires instead of the CMOS transistor itself [1].A solution is to replace the metal wires with optical fibers,which requires converting optical signals into electronic data by high performance photodetectors.Nanowire photodetectors are potential candidates for such applications since smaller device sizes are beneficial for high operating frequencies.Unfortunately,smaller sizes will reduce the light absorption and hence the photo sensitivity of photodetectors.