研究目的
To investigate the microscopic structure of uneven multiple quantum wells (MQWs) for AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) and to analyze their nonuniform quantum yields using cathodoluminescence spectroscopy.
研究成果
The study demonstrated an approach to approximating two-dimensional IQE analyses for uneven MQWs using CL mapping. The results support the model of localized current injection through Ga-rich stripe zones in the n-AlGaN cladding layer, which is consistent with the high IQEs observed in previous reports.
研究不足
The study acknowledges that the freeze-out of nonradiative recombination at 38 K was insufficient, particularly for the 265 nm MQW, which may lead to overestimation of IQE. The spatial resolution of CL mapping is limited by the excitation plume size and the diffusion length of minority carriers.
1:Experimental Design and Method Selection:
The study used cathodoluminescence (CL) mapping to analyze the microscopic structure of uneven MQWs. The CL measurements were performed at room temperature (300 K) and low temperature (38 K) to assess the nonuniform quantum yields.
2:Sample Selection and Data Sources:
The samples were AlGaN-based MQWs targeting electroluminescence wavelengths of 265 and 285 nm, grown on AlN templates with dense macrosteps.
3:List of Experimental Equipment and Materials:
A field-emission scanning electron microscopy (FE-SEM) system with a CL system was used, equipped with a sample holder for temperature control between 38 and 300 K. The electron beam acceleration voltage was set to 5 kV.
4:Experimental Procedures and Operational Workflow:
CL mapping was performed over a surface area of 2.5 × 2.5 μm2 at 50 nm intervals. SEM images were acquired before and after CL measurement to correct for drift.
5:5 × 5 μm2 at 50 nm intervals. SEM images were acquired before and after CL measurement to correct for drift.
Data Analysis Methods:
5. Data Analysis Methods: The CL intensity at 300 K relative to that at 38 K was analyzed to create an approximate map of internal quantum efficiency (IQE). The data were integrated over specific wavelength windows to eliminate signals from n-AlGaN cladding layers.
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