Carrier relaxation dynamics in SnxNy nanowires grown by chemical vapor deposition

Abstract

Carrier relaxation dynamics in tin nitride (SnxNy) nanowires have been investigated using femtosecond transient absorption spectroscopy. The nanowires were grown directly on quartz using chemical vapor deposition and had diameters 200 nm and lengths up to 2 μm. Steady state optical transmission measurements suggest that the band gap is ∼2.9 eV while time resolved measurements reveal that free carrier absorption dominates the carrier dynamics and overcomes state filling within 0.5 ps of the incoming excitation pulse even when probing above the band edge. This is a unique and markedly different behavior compared to what we have observed in other semiconductor nanowires and it is attributed to fast scattering of the photogenerated carriers out of the excitation energy region and possible rise in the lattice temperature due to energy relaxation. Carrier relaxation occurs through two channels with a fast time constants of ≈200 ps and a slow time constant ranging between 5 and 8 ns while intensity measurements reveal negligible contribution from nonlinear effects such as Auger recombination. © 2009 American Institute of Physics.