High quality factor nitride-based optical cavities: microdisks with embedded GaN/Al(Ga)N quantum dots

Area of Science:

• Materials Science
• Optoelectronics
• Quantum Dots

Background:

• Microdisk cavities are essential for photon confinement and light-matter interactions.
• Gallium nitride (GaN) quantum dots (QDs) are promising for optoelectronic applications.
• The choice of barrier material significantly impacts optical properties.

Purpose of the Study:

• To compare the quality factor (Q factor) of whispering gallery modes in microdisks incorporating GaN QDs grown on AlN versus AlGaN barriers.
• To investigate the influence of barrier material on optical losses in GaN QD-based microcavities.
• To correlate photoluminescence spectroscopy results with material properties.

Main Methods:

• Fabrication of microdisk (μ-disk) resonators with embedded GaN quantum dots (QDs).
• Room temperature photoluminescence (PL) spectroscopy to measure whispering gallery modes.
• Analysis of resonant mode spectra to determine quality factor values.
• Comparison of experimental results with theoretical simulations.

Main Results:

• High Q factor resonant modes were observed across the spectrum for both types of microdisks.
• GaN/AlN QD-based μ-disks exhibited significantly higher Q factors (Q>7000) compared to GaN/AlGaN QD-based μ-disks (Q up to 2000).
• The improved Q factor in AlN barrier samples is attributed to lower sub-bandgap absorption.

Conclusions:

• AlN barrier layers offer superior optical performance for GaN QD microdisk resonators compared to AlGaN barriers.
• The choice of barrier material is critical for minimizing cavity losses and enhancing light-matter interaction.
• These findings are crucial for developing high-performance optoelectronic devices based on GaN QDs.