Spin Injection and Relaxation in p-Doped (In, Ga)As/GaAs Quantum-Dot Spin Light-Emitting Diodes at Zero Magnetic Field
Author(s): Giba, AE (Giba, Alaa E.); Gao, X (Gao, Xue); Stoffel, M (Stoffel, Mathieu); Devaux, X (Devaux, Xavier); Xu, B (Xu, Bo); Marie, X (Marie, Xavier); Renucci, P (Renucci, Pierre); Jaffres, H (Jaffres, Henri); George, JM (George, Jean-Marie); Cong, GW (Cong, Guangwei); Wang, ZG (Wang, Zhanguo); Rinnert, H (Rinnert, Herve); Lu, Y (Lu, Yuan)
Source: PHYSICAL REVIEW APPLIED Volume: 14 Issue: 3 Article Number: 034017 DOI: 10.1103/PhysRevApplied.14.034017 Published: SEP 8 2020
Abstract: We report on efficient spin injection in p-doped (In, Ga)As/GaAs quantum-dot (QD) spin light-emitting diodes (spin LEDs) under zero applied magnetic field. A high degree of electroluminescence circular polarization (P-c)similar to 19% is measured in remanence up to 100 K. This result is obtained thanks to the combination of a perpendicularly magnetized Co-Fe-B/MgO spin injector allowing efficient spin injection and an appropriate p-doped (In, Ga)As/GaAs QD layer in the active region. By analyzing the bias and temperature dependence of the electroluminescence circular polarization, we evidence a two-step spin-relaxation process. The first step occurs when electrons tunnel through the MgO barrier and travel across the GaAs depletion layer. The spin relaxation is dominated by the Dyakonov-Perel mechanism related to the kinetic energy of electrons, which is characterized by a bias-dependent P-c. The second step occurs when electrons are captured into QDs prior to their radiative recombination with holes. The temperature dependence of P-c reflects the temperature-induced modification of the QD doping, together with the variation of the ratio between the charge-carrier lifetime and the spin-relaxation time inside the QDs. The understanding of these spin-relaxation mechanisms is essential to improve the performance of spin LEDs for future spin optoelectronic applications at room temperature under zero applied magnetic field.
Accession Number: WOS:000573673900003