Efficient generation of spin photocurrent by defect-mediated resonant excitation

Abstract

Spin current generators stand as pivotal components in spintronics-based information processing. In this work, defect-mediated spin photocurrent under inter-band excitation in unintentionally doped GaN has been studied by photon-energy dependent circular photogalvanic effect (CPGE) measurements. Resonant excitation with defect states could induce a giant spin photocurrent accompanying a relatively weak charge current. Photoexcited electrons in shallow Si-donor states cause a greater CPGE current compared to those in the conduction band (CB), which is presumed to stem from their extended feature as well as weaker momentum scattering. Besides, resonant excitation from defect-induced deep levels to CB yields a prominent CPGE current with a sign reversal. Given the localized nature of the deep level states, the photoexcited electrons with a mean momentum of zero induce this CPGE current due to the Rashba spin splitting of the CB. The defect-mediated CPGE shows promise for efficient spin current generators, aiding optoelectronic applications of spintronics.