Spin lifetimes in wurtzite InGaN/ GaN quantum disk-in-nanowire heterostructures from time resolved photoluminescence measurements

Spin-related phenomena in III-V semiconductors have been widely investigated to gain fundamental understanding of spin properties and control of carrier spins in semiconductor heterostructures. A detailed study of the manifestation of spin orbit coupling (SOC) and spin scattering processes in zinc blende structures like GaAs based materials has been already made. The spin lifetime (τ_s) is expected to be much larger in wurtzite GaN based semiconductors due to their weak SOC. However, there are only few reports on the measurement of spin relaxation in wurtzite GaN and their ternary compounds. Most of these^1-3 have been made with materials and heterostructures that have a large dislocation density. Interestingly, no output circular polarization is observed due to recombination of spin polarized carriers in InGaN/GaN quantum wells and this is attributed to poor crystalline quality and the presence of defects⁴. In this context, Ga(In)N nanowires grown by plasma-assisted molecular beam epitaxy⁵ (PA-MBE) provide an ideal platform for study of spin properties in GaN based materials as they are free of extended defects and have a small polarization field. We have performed polarized time-resolved photoluminescence (TRPL) measurements on InGaN quantum disks (QDs) in GaN nanowires for the first time. The measured spin relaxation time is ~100 ps, which is more than an order of magnitude larger than that in GaAs quantum wells.