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We report a high-power blue light-emitting diode (LED) with a high external quantum efficiency and low droop on a free-standing (20 2 1) GaN substrate. At a forward current of 20 mA, the LED showed a peak external quantum efficiency of 52% and an output power of 30.6 mW. In higher current density regions, the LED also showed outstanding performance, with droop ratios of 0.7% at 35 A/cm 2 , 4.3% at 50 A/cm 2 , 8.5% at 100 A/ cm 2 , and 14.3% at 200 A/cm 2. The output power and external quantum efficiency at 200 A/cm 2 were 266.5 mW and 45.3%, respectively.

We report indium incorporation properties on various nonpolar and semipolar free-standing GaN substrates. Electroluminescence characterization and x-ray diffraction (XRD) analysis indicate that the semipolar (202¯1¯) and (112¯2) planes have the highest indium incorporation rate among the studied planes. We also show that both indium composition and polarization-related electric fields impact the emission wavelength of the quantum wells (QWs). The different magnitudes and directions of the polarization-related electric fields for each orientation result in different potential profiles for the various semipolar and nonpolar QWs, leading to different emission wavelengths at a given indium composition.

We demonstrate high-efficiency green and yellow-green single-quantum-well light-emitting diodes (LEDs) grown on semipolar (20 21) GaN substrates by metal organic chemical vapor deposition. The output power and external quantum efficiency at a driving current of 20 mA under a pulsed condition with a 10% duty cycle are 9.9 mW and 20.4% for the green LED and 5.7 mW and 12.6% for the yellow-green LED, respectively. The electroluminescence linewidth narrowing, which is related to the band-filling effect caused by potential fluctuations, is not observed.

We demonstrate a small-area (0.1 mm 2 ) semipolar (20 2 1) blue (447 nm) light-emitting diode (LED) with high light output power (LOP) and external quantum efficiency (EQE) by utilizing a single 12-nm-thick InGaN quantum well. The LED had pulsed LOPs of 140, 253, 361, and 460 mW, and EQEs of 50.1, 45.3, 43.0, and 41.2%, at current densities of 100, 200, 300, and 400 A/cm 2 , respectively. The device showed little blue shift and had a narrow full width at half maximum (FWHM). Micro-electroluminescence (-EL) and scanning transmission electron microscope (STEM) images indicate a high-quality InGaN quantum well (QW) layer. #