Improved interface and dark current properties of InGaAs photodiodes by high-density N2 plasma and stoichiometric Si3N4 passivation

• Optimized passivation process by using high-density N 2 plasma and adjusting N 2 , SiH 4 flow and deposition temperature. • Interface state density decreases several times by using high-density N 2 plasma and adjusting N 2 and SiH 4 flow rates to 17 and 11 sccm. • Dark current can be reach 13 nA/cm 2 at 190 K and a −10 mV reverse bias by using high-density N 2 plasma and adjusting N 2 and SiH 4 flow rates to 17 and 11 sccm. • Surface current is negligible compared with the bulk current at room temperature. The interface and dark current properties of mesa-structure In 0.83 Ga 0.17 As photodiodes with improved passivation processes are investigated. Inductively coupled plasma chemical vapor deposition (ICPCVD) is used to continuously perform high-density N 2 plasma treatment of InGaAs epitaxial material and then SiN x passivation film deposition. The bonding efficiency between Si and N can be effectively improved when close-to-stoichiometric SiN x films are synthesized by precisely controlling the N 2 and SiH 4 flow rates. Metal-insulator-semiconductor (MIS) capacitors are fabricated to study the interface properties, and C-V analysis shows that the interface state density significantly decreases to 5.3 × 10 12 cm −2 eV −1 . Then, the process is applied to mesa-structure In 0.83 Ga 0.17 As photodiodes, and the results show a low dark current density (13 nA/cm 2 , @ 190 K) and negligible surface current (@ room temperature), indicating the ideal passivation effect. The method of increasing the deposition temperature to promote chemical bonding of SiN x films is studied, and both the interface and dark current properties can be improved. Our work is of important significance to the development of low-noise and large-format InGaAs arrays.