Comprehensive Structural Characterization Of Commercial Blue Light Emitting Diode By Using High-Angle Annular Dark Filed Scanning Transmission Electron Microscopy And Transmission Electron Microscopy

This study suggested comprehensive structural characterization methods for the commercial blue light emitting diodes(LEDs). By using the Z-contrast intensity profile of Cs-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM) images from a commercial lateral GaN-based blue light emitting diode, we obtained important structural information on the epilayer structure of the LED, which would have been difficult to obtain by conventional analysis. This method was simple but very powerful to obtain structural and chemical information on epi-structures in a nanometer-scale resolution. One of the examples was that we could determine whether the barrier in the multi-quantum well(MQW) was GaN or InGaN. Plan-view TEM observations were performed from the commercial blue LED to characterize the threading dislocations(TDs) and the related V-pit defects. Each TD observed in the region with the total LED epilayer structure including the MQW showed V-pit defects for almost of TDs independent of the TD types: edge-, screw-, mixed TDs. The total TD density from the region with the total LED epilayer structure including the MQW was about 3.6 x 10(8) cm(-2) with a relative ratio of Edge-: Screw-: Mixed-TD portion as 80%: 7%: 13%. However, in the mesa-etched region without the MQW total TD density was about 2.5 x 10(8) cm(-2) with a relative ratio of Edge-: Screw-: Mixed-TD portion of 86%: 5%: 9 %. The higher TD density in the total LED epilayer structure implied new generation of TDs mostly from the MQW region.