Fast spin relaxation in InGaN/GaN multiple quantum wells

Abstract

We report measurements of a fast spin relaxation in InGaN multi-quantum wells (MQW) using femtosecond circularly polarised pump -probe spectroscopy. These reveal quantum beats in the spin polarisation arising from a 1.6 meV fine structure splitting of the excitonic levels. We attribute this splitting to exchange interactions in the narrow quantum wells studied. The 5 K spin coherence time was measured to be 450 fs, a value which decreases by a factor of approximately two by 50 K.