Improvement in dark current characteristics and long-term stability of mesa InGaAs/InP p-i-n photodiodes with two-step SiN/sub x/ surface passivation

The authors report the successful fabrication of mesa In/sub 0.53/Ga/sub 0.47/As/InP p-i-n photodiodes passivated with SiN/sub x/ films. The SiN/sub x/ films were deposited by plasma-enhanced chemical vapor deposition in two steps. First, a thin SiN/sub x/ film was deposited at low temperature (50-150 degrees C) and then annealed at high temperature (250-350 degrees C) for 30-60 min to hydrogenate and nitridize the mesa surfaces simultaneously. Second, a thick SiN/sub x/ film was deposited at the annealing temperature to serve as a surface passivation and antireflective layer. Improvement in dark-current and long-term stability, compared to the results obtained from devices with one-step SiN/sub x/ surface passivation, has been achieved. The life tests at -20 V and 180/300 degrees C on these devices have shown a stable dark current for over 1500 h.<>