Strong surface passivation of GaAs nanowires with ultrathin InP and GaP capping layers

We demonstrate efficient surface passivation of GaAs nanowires using ultrathin in-situ grown epitaxial InP and GaP capping layers, with metallo-organic vapor phase epitaxy as the growth system. The passivation increased photoluminescence intensity by three orders of magnitude compared to unpassivated nanowires, and the effect remained strong after a month of storage in air. Effective passivation was acquired over a wide range of growth temperatures, although the highest studied temperatures caused additional detrimental effects such as etching and GaAsP formation. The capping layer thickness was in the order of few monolayers. Therefore, the impact on any other properties of the nanowires besides the surface states was minuscule. As a simple and effective method the studied capping layers offer an excellent way for nanowire passivation.