Characterization of InGaN/GaN multi-quantum-well blue-light-emitting diodes grown by metal organic chemical vapor deposition

Autor: K. S. Ramaiah, In-Gann Chen, Yan-Kuin Su, B. Kerr, H. P. Liu, Shoou-Jinn Chang
Rok vydání: 2004
Předmět:
Zdroj: Applied Physics Letters. 84:3307-3309
ISSN: 1077-3118
0003-6951
DOI: 10.1063/1.1728302
Popis: The structural, surface morphology, and the temperature dependence photoluminescence of InGaN~ 3n m!/GaN~ 7n m! 5 period multi-quantum-well blue-light-emitting diode ~LED! structures grown by metal organic chemical vapor deposition ~MOCVD! have been studied. Quantum dot-like structures and strain contrast evident by black lumps were observed in the quantum wells using high-resolution transmission electron microscopy ~HRTEM! analysis. Double-crystal high-resolution x-ray diffraction ~HRXRD! spectra of blue LED were simulated using kinematical theory method, to obtain composition, and period thickness of well and barrier. The ‘‘S’’ shape character shift as red‐blue‐redshift of the quantum-well emission line, i.e., blue emission peak 2.667 eV at 10 K, was observed with variation of temperature in the photoluminescence ~PL! spectra. The shift is assigned to the potential fluctuations due to alloy inhomogeneous distribution in the quantum wells. The In composition in the quantum wells obtained by two independent techniques, namely HRXRD and PL, was 8% and 19%, respectively. The reason for this large difference in composition is explained in this letter. © 2004 American Institute of Physics. @DOI: 10.1063/1.1728302# Nitride-based blue and green light-emitting diodes illuminating with high brightness are now commercially available, despite high dislocation density of 10 8 ‐1 0 9 cm 22 in the epilayers. 1 The InGaN/GaN multi-quantum-well structures are being used as active layers in the light-emitting diodes ~LED! because the emission spectrum can be tailored from ultraviolet to visible region by varying In composition. The blue LEDs, which showed higher efficiency than that of green LEDs, have been widely used in the communication and information technologies. The In mole fraction of 0.1‐ 0.2 and 0.45 is required for blue and green LEDs, respectively. The phase separation or segregation of In is a major problem in the InGaN system due to solid phase immiscibility between InN and GaN. This segregation is due to a large difference in interatomic spacing, and other physical properties such as thermodynamical and chemical instabilities, etc., which are very different between InN and GaN. The experimental and theoretical studies revealed that the solid-phase immiscibility is high in InGaN. 2 At normal growth tempera
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