Strong suppression of surface recombination in InGaAs nanopillars

Summary form only given. In this work, we report a remarkable suppression of the surface recombination rates in passivated III-V undoped InGaAs nanopillars on InP (inset of Fig. 1a). The surface passivation comprises ammonium sulfide, (NH4)2S, chemical treatment followed by encapsulation with a 50 nm layer of SiOx by plasma-enhanced chemical vapor deposition performed at 300°C. Before passivation, fabricated nanopillars with -300 nm lateral width, d, show a very poor photoluminescence (PL) emission (blue curve in Fig. 1a). The corresponding carrier dynamics, measured by time-correlated single-photon counting, Fig 1b, reveal an extremely short lifetime of ~130 ps, related to the well-known strong surface recombination velocity at InGaAs surfaces [3]. After the sulfur treatment followed by SiOx, we observe a substantial increase by almost two orders of magnitude of the PL intensity (red curve in Fig. 1a), while the carrier lifetime increases by more than two orders of magnitude to a value ~23 ns, red curve in Fig 1b. The estimated surface recombination velocity, S, decreases from about 2×104 cm/s in the untreated nanopillars down to around 260 cm/s (inset of Fig. 1b). To our knowledge, this is a record low value in undoped InGaAs semiconductors. Most importantly, our passivation studies reveal that the SiOx capping layer not only protects the pillars' sidewalls against oxidation, as reported in [5], but actively takes part in the passivation process, a result never previously reported.