High-Brightness 350 nm Ultraviolet InAlGaN Light Emitting Diodes on Si(111) Substrate with Transparent AlN/AlGaN Buffer Structure

We report on high brightness ultraviolet (UV) light emitting diodes (LEDs) with an InAlGaN/AlGaN multi quantum well (MQW) on a Si(111) substrate emitting around 350 nm. With high indium contents up to 10% in the quaternary alloy InAlGaN well layers, strong UV emission is obtained in cathode-luminescence and photoluminescence measurements. With a novel AlN/AlGaN superlattices (SLs) buffer, a crack-free, low dislocation AlGaN cladding layer is expitaxially grown on a Si(111) substrate. By combining the quaternary InAlGaN well with a high indium content and the high quality AlGaN cladding layer on the AlN/AlGaN SLs, the InAlGaN/AlGaN MQW exhibits very high internal quantum efficiency of 15% at around 350 nm. The UV LED on Si(111) emits at a peak emission wavelength of 350.9 nm at 20 mA driving current. The maximum UV output power of the LED is 3.9 times as high as that without indium in the well.