We investigate the effects of pixel distance and light emitting diode (LED) thickness on the luminance distribution and contrast ratio of a 16 × 16 blue and white LED array for vehicle headlamp application. With increasing pixel distance from 10 to 20 μm, the contrast ratio increased from 33:1 to 51:1 for white LEDs and from 37:1 to 48:1 for blue LEDs. As the LED thickness decreased from 4.5 to 2.0 μm, the contrast ratio increased from 37:1 to 62:1 for blue LEDs and from 33:1 to 97:1 for white LEDs. The blue LEDs fabricated with ultrathin-GaN and self-aligned Si barrier showed the contrast ratio of 48:1 and 39:1, respectively, while the white LEDs with ultrathin-GaN and self-aligned Si barrier yielded the contrast ratio of and 89:1 and 99:1. Further, LEDs with the self-aligned Si barrier had better luminance uniformity than those with the ultrathin-GaN. LED array with the self-aligned Si barrier exhibited narrower dark space than that with the ultrathin-GaN. At 60 mA, the LED with the self-aligned Si barrier gave 6% higher light output than that with the ultrathin-GaN. A headlamp unit using 16 × 16 LED array was demonstrated with the Si self-aligned barrier.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials