Electron spin relaxation in X-valley of indirect bandgap AlxGa1-xAs: A new horizon for the realization of next generation spin-photonic devices

Abstract

GaAs/AlGaAs quantum well (QW) system is utilized to investigate the electron spin relaxation in the satellite X-valley of indirect band gap Al0.63Ga0.37As epitaxial layers through polarization resolved photo-luminescence excitation spectroscopy. Solving the rate equations, steady state electronic distribution in various valleys of AlxGa1-xAs is estimated against continues photo carrier generation and an expression for the degree of circular polarization (DCP) of photoluminescence coming from the adjacent quantum well (QW) is derived. Amalgamating the experimental results with analytical expressions, the X-valley electron spin relaxation time (τ_S^X) is determined to be 2.7 +/- 0.1 ps at 10 K. To crosscheck its validity, theoretical calculations are performed based on Density Functional Theory within the framework of the projector augmented wave method, which support the experimental result quite well. Further, temperature dependence of τ_S^X is studied over 10-80 K range, which is explained by considering the intra-valley scattering of carriers in the X-valley of indirect band gap AlGaAs barrier layer. It is learnt that the strain induced modification of band structure lifts the degeneracy in X-valley, which dominates the electron spin relaxation beyond 50 K. Furthermore, the DCP spectra of hot electrons in indirect band gap AlGaAs layers is found to be significantly different compared to that of direct bandgap AlGaAs. It is understood as a consequence of linear k dependent Dresselhaus spin splitting and faster energy relaxation procedure in the X-valley. Findings of this work could provide a new horizon for the realization of next generation spin-photonic devices which are less sensitive to Joule heating.

arXiv comment25 pages, 8 figures

References in corpus (15)

• Spin dynamics in semiconductors
• Ultrafast spin-lasers
• Optical spin injection and spin lifetime in Ge heterostructures
• Pure circular polarization electroluminescence at room temperature with spin-polarized light-emitting diodes
• Optical orientation of electron spins in GaAs quantum wells
• Spin-flip Raman scattering of the $\Gamma$-X mixed exciton in indirect band-gap (In,Al)As/AlAs quantum dots
• A spin light emitting diode incorporating ability of electrical helicity switching
• Spin dynamics in a compound semiconductor spintronic structure with a Schottky barrier
• Optical orientation and alignment of excitons in direct and indirect band gap (In,Al)As/AlAs quantum dots with type-I band alignment
• Spin dynamics and magnetic-field-induced polarization of excitons in ultrathin GaAs/AlAs quantum wells with indirect band gap and type-II band alignment
• Dynamic polarization of electron spins interacting with nuclei in semiconductor nanostructures
• Spin-orbit coupling in bulk GaAs
• Spin Polarization via Electron Tunneling through an Indirect-Gap Semiconductor Barrier
• L-valley Electron Spin Dynamics in GaAs
• Real-time modelling of Optical orientation in GaAs: generation and decay of the degree of spin polarization