A 110 mW AlGaN-based UV lamp emitting at 278 nm

We report record output power of deep ultraviolet (UV) LEDs with peak emission at 278 nm. These new light sources are expected to find numerous applications in air, water and surface sterilization/decontamination, bio-agent detection and identification, UV curing, biomedical and analytical instrumentation, etc. Recently we reported breakthrough in AlGaN-based deep UV LEDs with wallplug efficiency approaching 1%.' We will describe further improvements in the device design and processing for a better control of strain and carrier injection. These improvements yielded approximately 30% higher CW output powers close to 1. I mW at 20 mA current and 2 mW at 50 mA. The devices exhibit narrow emission line with FWHM of 11 nm and very high peak to stray light ratio close to 4 orders of magnitude, which to our knowledge is the best ratio ever reported for deep UV LEDs. We developed packaging solution for power combining of multiple deep UV LED chips with efficient heat dissipation. The UV lamp was made from 16 LEDs chips combined into 8x2 LED array in the form of 8 branches connected in parallel and each branch containing two LEDs connected in series. The lamp emitted at 278 nm and produced a continuous-wave power in excess of 11 mW at 200 mA. Under pulse operation the maximum power exceeding 110 mW was obtained at 1.9 A driving current. These are the highest CW and pulsed output power levels achieved in deep UV range.