研究目的
Investigating the effects of aperture size on the performance of semipolar GaN-based vertical-cavity surface-emitting lasers (VCSELs) with buried tunnel junction (BTJ) current apertures under continuous wave operation.
研究成果
The study demonstrated semipolar VCSELs with BTJ defined apertures under continuous wave operation, achieving a differential efficiency of 4% and a threshold current of 2.7 mA. The effects of aperture diameter on differential efficiency and threshold current density were presented, showing that differential efficiency increased with aperture size while threshold current density remained constant for apertures larger than 10 μm. Filamentary lasing in larger apertures was suggested to be due to current injection nonuniformity, supported by nearfield and thermal imaging.
研究不足
The study notes that the devices suffered from high operating voltage due to incomplete activation and abnormally high roughness, which introduced significant scattering loss. The mechanism for minor degradation in device performance under continuous wave operation was not identified.
1：Experimental Design and Method Selection:
The study involved the design and testing of semipolar GaN-based VCSELs with BTJ defined apertures. The methodology included the use of atmospheric metal-organic chemical vapor deposition (MOCVD) for epitaxial growth, reactive ion etching (RIE) for defining apertures, and ion beam deposition (IBD) for mirror deposition.
2：Sample Selection and Data Sources:
Devices with apertures ranging from 6 μm to 16 μm were tested across the sample to study the effect of aperture size on lasing performance.
3：List of Experimental Equipment and Materials:
Equipment included MOCVD for epitaxial growth, RIE for etching, and IBD for mirror deposition. Materials included GaN substrates and various layers of GaN and AlGaN for the device structure.
4：Experimental Procedures and Operational Workflow:
The procedure involved epitaxial growth, aperture definition via etching, device fabrication, and testing under continuous wave and pulsed operation.
5：Data Analysis Methods:
Data analysis included measuring light-current-voltage (LIV) characteristics, thermal imaging, and nearfield imaging to assess device performance and mode behavior.
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