High-power UV LEDs beat 1mW
Andy Allerman (pictured) led the semiconductor material growth activity for the project. The device has layers of aluminium gallium nitride (AlGaN) deposited on a sapphire (Al2O3) substrate.
Adding aluminium to GaN creates a shorter output wavelength. The mix for the 275nm device contained around 50% Al. However, adding Al makes the material harder to grow and reduces the ability of electric current to flow through the material.
Key to the Sandia devices has been growing material of sufficient quality. Flip-chip packaging also contributed to improved performance. The finished LED is a bottom-emitting device that uses a transparent buffer layer and substrate.
"Emission wavelengths of 275-290nm with such high power outputs is a major breakthrough in UV LED development," says Bob Biefeld, manager of Sandia’s Chemical Processing Science department.
Sandia highlights possible applications for biological agent detection, non-line-of-sight (NLOS) covert communications, water purification and polymer curing.