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 high power yellow InGaN single-quantum-well light-emitting diodes (LEDs) with a peak emission wavelength of 562.7nm grown on low extended defect density semipolar (112¯2) bulk GaN substrates by metal organic chemical vapor deposition. The output power and external quantum efficiency at drive currents of 20 and 200mA under pulsed operation (10% duty cycle) were 5.9mW, 13.4% and 29.2mW, 6.4%, respectively. It was observed that the temperature dependence of the output power of InGaN LEDs was significantly smaller than that of AlInGaP LEDs.
Growth conditions for AlN in two dimensional (2D) and three dimensional (3D) growth modes were explored on SiC using metal organic chemical vapor deposition. High quality AlN layers were obtained by alternating between 3D and 2D growth modes, referred to as modulation growth (MG). Long parallel atomic terraces without step terminations were observed in atomic force microscopy (AFM) scans of MG AlN, indicating a reduced dislocation density. X-ray diffraction rocking curves yielded full widths at half maximum (FWHM) of 86 and 363arcsec for the (002) and (102) reflections, respectively, giving further evidence of low dislocation density in the film. 3D-2D MG also releases some of the tensile strain in the AlN film, enabling the growth of thick, crack-free AlN on SiC substrates.
Blue InGaN∕GaN multiple-quantum-well light emitting diodes with a peak emission wavelength of 444nm were grown on low extended defect density semipolar (101¯1¯) bulk GaN substrates by conventional metal-organic chemical vapor deposition. The calculated external quantum efficiency and output power at a drive current of 20mA under pulsed operations (10% duty cycle) were 29% and 16.21mW, respectively. The device exhibited virtually no peak electroluminescence wavelength shift with increasing drive currents, indicating a significant reduction of polarization-related internal electric fields.
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