Optical polarization of m-plane In-GaN/GaN light-emitting diodes characterized via confocal microscope

A confocal microscope was applied to characterize near-field optical polarization of light emission from InGaN-based light-emitting diodes prepared on a nonpolar orientation. Detection of stray light was significantly reduced as a result of the confocal technique compared to broad-area measurements. The confocal measurement required no special sample preparation and obtained data was directly interpretable. A polarization ratio of 0.83 was measured on long-wavelength emitting devices and was sustained over two orders of magnitude of low current range. Energy shifts and separation of emission peaks for the two polarization components were evaluated to discuss the valence-band structure. Energy shifts indicated that the topmost band vertical bar X > had a heavier effective mass than the lower band vertical bar Z >. Splitting energy of InGaN was estimated to be 30 meV. Results were consistent with the past reports, thus it was confirmed that the confocal microscope is a valid technique to characterize near-field optical polarization. [GRAPHICS]