Surface passivation of InAs avalanche photodiodes for low-noise infrared imaging

The effect of surface passivation on the etched-mesa InAs diodes was investigated by carrying out the fabrication and passivation of InAs diodes. Extensive and detailed current-voltage characterization was done to determine the most suitable type of insulating material for the surface passivation. SU-8, silicon nitride, silicon dioxide and B-staged Bisbenzocyclobutene were used for the purpose of minimizing the conductivity of the etched mesa surface of InAs diodes. The forward- and reverse-biased characteristics of InAs diodes were measured at room temperature and 77 K in order to carefully investigate the effect of different surface passivation schemes. The results of this work categorically indicated that SU-8 is the most effective surface passivation material for InAs diodes, whereas silicon nitride and silicon dioxide have contributed to an even higher surface leakage current. Furthermore, SU-8 passivated InAs diodes were more sustainable to high bias voltages and its robustness increases the opportunity of its utilization for practical applications such as infrared imaging.