The photodiode device structure, which has developed almost simultaneously with Si based p-n junctions, has had a dramatic impact on everyday life, especially in the field of communication and sensing. The last few decades have seen optical techniques come to dominate long-haul communication and photodiode technologies, serving as an energy transducer in the receiver end, which can convert optical data into electrical signals for further processing. In addition to communication, photodiodes have also found some killer applications in advanced high-speed image systems and will eventually replace traditional slow charge-coupled devices (CCD)
