Study on spin and optical polarization in a coupled InGaN/GaN quantum well and quantum dots structure

Area of Science:

• Semiconductor Physics
• Spintronics
• Quantum Optics

Background:

• Investigating spin and optical polarization in semiconductor nanostructures is crucial for advanced electronic and photonic devices.
• Coupled quantum well (QW) and quantum dot (QD) systems offer unique properties for spin manipulation.
• Efficient spin injection and long spin lifetimes are key challenges in spintronic applications.

Purpose of the Study:

• To investigate the spin and optical polarization characteristics of a coupled InGaN/GaN quantum well (QW) and quantum dot (QD) structure.
• To explore the mechanism of spin-conserved tunneling for spin injection from QW to QDs.
• To evaluate the potential of this coupled structure for realizing efficient spin-polarized light sources.

Main Methods:

• Fabrication and characterization of a coupled InGaN/GaN QW and QD structure.
• Optical spin-injection and -detection techniques.
• Photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements.

Main Results:

• Demonstrated temporary storage of spin-electrons in the QW and spin injection into QDs via spin-conserved tunneling.
• Achieved a higher circular polarization degree (CPD) of ~49.1% compared to single-layer QD structures.
• Extended spin relaxation time to approximately 2.43 ns due to suppressed spin relaxation and weaker state-filling effects.

Conclusions:

• The coupled InGaN/GaN QW/QD structure effectively suppresses spin relaxation and enhances optical polarization.
• Spin-conserved tunneling is a key mechanism for efficient spin injection and prolonged spin lifetime.
• This structure shows significant promise as a candidate for developing advanced spin-polarized light sources.