In situ passivation of GaAsP nanowires

We report on the structural and optical properties of GaAsP nanowires (NWs) grown by molecularbeamepitaxy. By adjusting the alloy composition in theNWs, the transition energy was tuned to the optimal value required for tandem III-V/silicon solar cells. We discovered that an unintentional shell was also formed during the GaAsP NW growth. The NW surface was passivated by an in situ deposition of a radial Ga(As) P shell. Different shell compositions and thicknesses were investigated. We demonstrate that the optimal passivation conditions for GaAsP NWs (with a gap of 1.78 eV) are obtained with a 5 nm thick GaP shell. This passivation enhances the luminescence intensity of the NWs by 2 orders of magnitude and yields a longer luminescence decay. The luminescence dynamics changes from single exponential decay with a 4 ps characteristic time in non-passivated NWs to a biexponential decay with characteristic times of 85 and 540 ps in NWs with GaP shell passivation.