Spin-dependent photocurrent induced by Rashba-type spin splitting in Al0.25Ga0.75N/GaN heterostructures

Circular and linear photogalvanic effects are experimentally demonstrated in (0001)-oriented Al(0.25)Ga(0.75)N/GaN heterostructures. By changing the incident angle of the pumping light beam, it is possible to manipulate the relative strength between the circular and linear photogalvanic effects. The spin-dependent signal is evidenced by the sign change upon reversing the radiation helicity. Its consistency with the strength of the Rashba-type spin splitting as determined from the beating of Shubnikov-de Haas oscillations reveals the underlying mechanism responsible for the observed effect. The measured spin-dependent photocurrent is larger than that of the intersubband transition by two orders of magnitude at room temperature. AlGaN/GaN heterostructures therefore provide an excellent opportunity for the generation of spin polarized current to be used in spintronics.