Spin Injection and Relaxation in p -Doped ( In , Ga ) As / Ga As Quantum-Dot Spin Light-Emitting Diodes at Zero Magnetic Field

Alaa E Giba (1) , Xue Gao (1) , Mathieu Stoffel (1) , Xavier Devaux (1) , Bo Xu (2) , Xavier Marie (3) , Pierre Renucci (3) , Henri Jaffrès (4) , Jean-Marie George (4) , Guangwei Cong (5) , Zhanguo Wang (2) , Hervé Rinnert (1) , Yuan Lu (1)

1 IJL - Institut Jean Lamour
2 LSMS - Key Laboratory of Semiconductor Materials Science
3 LPCNO - Laboratoire de physique et chimie des nano-objets
4 Laboratoire Albert Fert (ex-UMPhy Unité mixte de physique CNRS/Thales)
5 AIST - National Institute of Advanced Industrial Science and Technology

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) ∼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.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Alaa E Giba, Xue Gao, Mathieu Stoffel, Xavier Devaux, Bo Xu, et al.. Spin Injection and Relaxation in p -Doped ( In , Ga ) As / Ga As Quantum-Dot Spin Light-Emitting Diodes at Zero Magnetic Field. Physical Review Applied, 2020, 14 (3), ⟨10.1103/PhysRevApplied.14.034017⟩. ⟨hal-02999545⟩