by Steven Keeping @ digikey.com:
The dominant technology for today’s high-brightness LEDs is gallium nitride (GaN) on sapphire or silicon carbide (SiC) substrates. These materials are popular because the resultant LEDs are bright, efficient, and last a long time. However, the chips are tough to manufacture and package into useable devices, multiplying the cost of end products that use them as light engines. Although prices have plummeted in recent years, LED lighting is still considerably more expensive to purchase than traditional alternatives. This initial expense is cited as a major factor slowing the acceptance of solid-state lighting (SSL).
A pioneering group of manufacturers has worked hard to reduce the cost of high-power LEDs by replacing the sapphire or SiC substrate with silicon (Si), the material routinely used to manufacture most electronic chips (“ICs”). The key benefit is a very-low-cost supply of wafers and the opportunity to use depreciated 8-inch wafer fabs for LED manufacture. Combined, those concepts enable a dramatic reduction in LED prices, overcoming consumer objections.
Improved Silicon-Substrate LEDs Address High Solid-State Lighting Costs – [Link]