研究目的
Investigating the internal quantum efficiencies of AlGaN quantum dots grown by molecular beam epitaxy and emitting in the UVA to UVC ranges.
研究成果
The study demonstrates the potential of AlyGa1?yN QDs as efficient UV emitters, with IQE values between 5% and 20% at room temperature for QDs emitting in the 276–308 nm range. The highest IQE values were found for QDs with higher Al content y, indicating their suitability for deep UV applications despite high dislocation densities.
研究不足
The study is limited by the high threading dislocation densities in the samples, which can affect the internal quantum efficiency. Additionally, the complexity of QD samples with inhomogeneous distributions of defects and QDs poses challenges in accurately determining the IQE.
1：Experimental Design and Method Selection:
The study involved growing AlyGa1?yN quantum dots (QDs) by molecular beam epitaxy (MBE) on AlxGa1?xN (0001) using a 2-dimensional–3-dimensional growth mode transition. The influence of the active region design, including composition y, QD height, and bandgap difference between the QDs and the cladding layer, was investigated.
2：Sample Selection and Data Sources:
Samples were grown on (0001) sapphire substrates by MBE, with AlyGa1?yN QDs formed for Al compositions y varying between 10% and 40%.
3：0%. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: A RIBER 32 reactor was used for MBE growth, with solid sources for the III-elements and ammonia (NH3) as the nitrogen precursor, except for the QD layers which used a RIBER RF nitrogen (N2) plasma source.
4：Experimental Procedures and Operational Workflow:
The structure layout included a low-temperature GaN buffer layer, followed by AlN and AlxGa1?xN layers, and then the QD layer formation. PL and TRPL measurements were performed to analyze the optical properties.
5：Data Analysis Methods:
The IQE at LT was estimated from TRPL experiments, and the PL spectrally integrated intensity ratios between RT and LT were measured to estimate the IQE at RT.
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