SSLs use semiconductor light-emitting diodes (“LEDs”), polymer light-emitting diodes (“PLEDs”), organic light-emitting diodes (“OLEDs”), or other types of solid state emitters (SSEs) as sources of illumination. Generally, SSLs generate less heat, provide greater resistance to shock and vibration, and have longer life spans than conventional lighting devices that use filaments, plasma, or gas as sources of illumination (e.g., florescent or incandescent lights). SSL devices are increasingly in demand for many purposes because such devices efficiently produce high-intensity, high-quality light. Mobile phones, personal digital assistants, digital cameras, MP3 players, and other portable devices use SSLs, such as white light SSLs, for background illumination. The possible applications for SSL devices extend beyond portable devices and include ceiling panel lights, desk lamps, refrigerator lights, table lamps, street lights, automobile headlights, and many other lighting applications.
White light is desirable for many applications, but current SSLs cannot directly produce white light. One conventional technique for emulating white light from an SSL includes depositing a converter material (e.g., a phosphor) on a light emitting material. For example, as shown in FIG. 1A, a conventional SSL device 10 includes a support 2 carrying an LED die 4 and a converter material 6 deposited on the LED die 4. The LED die 4 can include one or more light emitting components. For example, as shown in FIG. 1B, the LED die 4 can include a silicon substrate 12, an N-type gallium nitride (GaN) material 14, an indium gallium nitride (InGaN) material 16 (and/or GaN multiple quantum wells), and a P-type GaN material 18 on one another in series. The LED die 4 can also include a first contact 20 on the P-type GaN material 18 and a second contact 22 on the N-type GaN material 14. Referring to both FIGS. 1A and 1B, in operation, the InGaN material 16 of the LED die 4 emits a blue light that stimulates the converter material 6 to emit a light (e.g., a yellow light) at a desired frequency. The combination of the blue and yellow emissions appears white to human eyes if matched appropriately.
Another conventional construction of an SSL device 20 is shown in FIG. 2. The device 20 has a support 23 upon which an LED 24 is mounted. The device 20 also includes a phosphor well 26 containing a converter material and a lens 28 formed over the LED 24. This configuration produces light primarily focused in a direction 29 perpendicular to the LED 24. The lighting distribution from this arrangement is suitable for some lighting applications. However, many other applications can benefit from a more dispersed angular distribution of light. Accordingly, there remains a need for SSL devices that produce multi-directional light patterns.