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Fig. 5.1. Parabolic electron and hole dispersion relations showing “vertical” electronhole recombination and photon emission.
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Fig. 5.2. Theoretical emission spectrum of an LED. The full width at half maximum (FWHM) of the emission line is 1.8 kT.
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Fig. 5.3. (a) Definition of the escape cone by the critical angle Phi c . (b) Area element dA. (c) Area of calotte-shaped section of the sphere defined by radius r and angle Phi c.
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Fig. 5.4. Geometrical model used to derive the Lambertian emission pattern. (a) The light emitted into angle phi f inside the semiconductor is emitted into the angle d Phi in air. (b)Illustration of the area element dA of the calotte-shaped section of the sphere.
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Fig. 5.5. Light-emitting diodes with (a) planar, (b) hemispherical, and (c) parabolic surfaces. (d) Far-field patterns of the different types of LEDs.
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Fig. 5.6. (a) LED without and (b) with dome-shaped epoxy encapsulant. A larger escape angle is obtained for the LED with an epoxy dome. (c) Calculated ratio of light extraction efficiency emitted through the top surface of a planar LED with and without an epoxy dome.
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Fig. 5.7. Characteristic temperature T1 of GaInN/GaN blue, GaInN/GaN green, and AlGaInP/GaAs red LEDs near room temperature (after data from Toyoda Gosei Corp., 2000).
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