| Summary: | 碩士 === 國立中央大學 === 光電科學研究所 === 98 === Light emitting diodes (LEDs) have various advantages such as small size, long life and good reliability. However, the light intensity distribution of native planar LED chips performed a Lambertian light pattern in spatial distribution. It caused the light intensity decay with viewing angle by cosine law. When LED emitting far-field pattern in the Lambertian formation, it became a weakly directional and non-uniform light source. In this thesis, we modulated the light pattern of LED chip, by the e-beam lithography and the dry etching processes integrated with LED chip process. Under this process integration, the 1-D sub-micron grating was fabricated on the chip surface to achieve the modulation of LEDs chip light pattern.
The light extraction enhancement was increased by the interaction between the emitting photon and the 1-D grating structure and the light pattern was also modulated. Five different periods of 1-D grating were designed (0.3 μm, 0.5 μm, 0.75 μm, 1.0 μm and 2.0 μm), and the angle-resolved measurements were completed under two luminescence mechanisms: the photoluminescence (PL) and the electroluminescence (EL).The results showed that the size of grating period affected the light patterns transition. In PL measurement, the grating period with 0.5μm, enhanced the light intensity at the observing angle of ±25°; the grating period with 2.0 μm, performed a light intensity in uniform between the observing angle of ±60°. The results of EL measurement were similar to that of PL. Furthermore, the effects of stimulated emission and spontaneous carrier recombination light pattern were evaluated by the FDTD analysis. The simulation results combined with different luminescence cases and the optics phenomenon resulted from the 1-D grating such as the scatter and the diffraction were used to discuss the relationship between the size of 1-D grating period, the far-field light patterns.
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