研究目的
Investigating the electron-nuclei hyperfine interaction in indirect band gap (In,Al)As/AlAs quantum dots with type-I band alignment.
研究成果
The study successfully determined the hyperfine constants for the As, In, and Al nuclei in the X valley of (In,Al)As/AlAs quantum dots, revealing that only the As nuclei have a strong interaction with the electron spin in the X valley. This interaction results in a considerable narrowing of the Hanle curve compared to that of Γ excitons.
研究不足
The study is limited by the accuracy of the QD size determination, which does not exceed 25%, and the assumption that the polarization of the PL equals the electron spin polarization, neglecting the hole spin polarization.
1：Experimental Design and Method Selection:
The study involved measuring the polarization degree of the photoluminescence in a transverse magnetic field (Hanle effect) and the polarization recovery in a longitudinal magnetic field to study the electron-nuclei hyperfine interaction.
2：Sample Selection and Data Sources:
Self-assembled (In,Al)As quantum dots embedded in an AlAs matrix were grown by molecular-beam epitaxy on a semi-insulating (001)-oriented GaAs substrate.
3：List of Experimental Equipment and Materials:
A JEM-4000EX system for TEM, an electromagnet for generating weak magnetic fields, a Q-switched Nd:YVO4 pulsed laser for nonresonant excitation, and a tunable continuous-wave Ti:sapphire laser for selective excitation.
4：Experimental Procedures and Operational Workflow:
The photoluminescence was excited either nonresonantly or selectively, and the emission was detected using a liquid-nitrogen-cooled CCD camera or a silicon avalanche photodiode.
5：Data Analysis Methods:
The circular polarization degree was determined, and the Hanle and polarization recovery curves were analyzed to extract the hyperfine interaction constants.
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