Figure 1
There are promising developments in semiconductor processes using gallium nitride (GaN) to make brighter-output LEDs and power devices. Two recent breakthroughs highlight this potential.
Bridgelux Inc., a developer of LED light sources, has demonstrated an LED with a light output of 135 lm/W by growing GaN on a silicon wafer. The company calls it the first achievement of commercial-grade performance from a silicon substrate LED. The 1.5-mm diameter LED operates at 2.9 V and is driven at 350 mA with a color-corrected temperature (CCT) of 4730K.
Bridgelux believes this process will deliver a 75% improvement in LED manufacturing costs. The company foresees optimization of the epitaxial process it’s using on 200-mm (8-in.) silicon wafers and anticipates the first commercially available products on the market within the next two to three years.
On another front, scientists at North Carolina State University have devised a technique to boost high-power potentials for GaN power devices that are more energy-efficient than existing technologies when exposed to high voltages. They solved the problem of high-voltage breakdowns in GaN devices with increasing voltage levels by implanting a buffer made of argon at the edges of the GaN device (see the figure).
This technique has allowed the device to handle 10 times as much power than previously possible. The buffers spread out the electric field that would normally be created when a GaN device is subjected to high voltages at specific points at the device’s edge, effectively destroying the device.
The scientists tested the new technique on conventional Schottky diodes and found that the argon implant allowed the GaN diodes to handle voltages that were almost seven times higher. “By improving the breakdown voltage from 250 to 1650 V, we can reduce the electrical resistance of these devices a hundred-fold,” says Jay Baliga, distinguished professor of electrical and computer engineering at the university.