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

Abstract

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 |X 〉 had a heavier effective mass than the lower band |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. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of off-axis GaN substrates on optical properties of m-plane InGaN/GaN light-emitting diodes

“…The electroluminescence (EL) properties were measured through the GaN substrate onto a Si photodiode. The optical polarization of the LEDs was measured by using confocal microscope at surface-normal detection [17]. Photoluminescence (PL) measurements were performed at room temperature (RT) using the 325 nm line of a He-Cd laser.…”

Optical polarization characteristics of InGaN∕GaN light-emitting diodes fabricated on GaN substrates oriented between (101¯) and (101¯1¯) planes

“…8. This optical microscope enables small-area detection ͑compared to the light-emitting area of approximately 300 ϫ 300 m 2 ͒ and minimizes the detection of stray light ͑i.e., reflected or refracted light͒.…”

Effects of Growth Temperature and Postgrowth Annealing on Inhomogeneous Luminescence Characteristics of Green-Emitting InGaN Films

“…10,11 The standard V-2A filter cube selects the wavelength range (380 nm to 420 nm) of illumination generated by a metal halide lamp. With a 1009 objective lens (numerical aperture 0.90), the illumination intensity was 7 W/cm 2 at the sample.…”