336 nm ultraviolet LEDs grown with AlN interlayers for strain reduction

摘要

UV LEDs with a peak emission wavelength of 336 nm were grown on a gallium nitride/sapphire substrate by inserting an AlN interlayer to prevent cracking. A maximum output power of 44 μW was achieved at 100 mA DC for 200 x 200 μm die wirebonded to a header and encapsulated in epoxy. The maximum output power increased to 0.367 mW at 537 mA when tested under pulsed conditions. Lateral current crowding and device self-heating are observed to be the major factors limiting output power. We have shown that epoxy packaging traditionally used for InGaN based LEDs has strong absorption at these wavelengths and will not be suitable for deep UV LEDs.