Passivation of InAs/GaSb type II superlattice photodiodes

One of the major challenges faced by antimonide-based devices is a result of the large number of surface states that are generated. Surface passivation and subsequent capping of the surfaces are essential for any practical applicability of this material system, as evidenced by the comparison of unpassivated and passivated InAs/GaSb superlattice mid-infrared photodiodes herein. The surface passivation methods include silicon dioxide (SiO2) coating after anodic sulfide, SiO2 coating after anodic oxide, SiO2 coating only, zinc sulfide (ZnS) coating after anodic sulfide, and ZnS coating after ammonium sulfide [(NH4)2S] chemical passivation. The leakage current as a function of bias voltage (I–V) for superlattice diodes obtained using different passivation methods has been examined at 77 K. The best performance was demonstrated by the SiO2 after anodic sulfide passivation. The leakage current of the passivated diode is four orders of magnitudes less than that of the unpassivated diode.