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Improved performance of AlGaN-based deep ultraviolet light-emitting diodes with n-AlGaN underlayers

We demonstrate notable performance improvement of 270 nm deep ultraviolet light-emitting diodes (DUV-LEDs) by inserting an n-AlGaN underlayer (UL), which was directly beneath an AlGaN multiple quantum well (MQW) active region. This DUV-LED exhibited significantly improved forward and reverse bias current-voltage characteristics, and spectral properties. As a result, the turn-on voltage was decreased from 7 to 4.6 V by introducing the n-AlGaN UL, and the maximum light output power and external quantum efficiency of DUV-LEDs with the n-AlGaN UL, obtained via on-wafer measurement, were increased by factors of 3.6 and 2.2, respectively. Further enhancements can be realized by using high-quality AlN/sapphire templates together with the n-AlGaN UL. These improvements were considered to be attributed to the introduction of the n-AlGaN UL which improved electron injection and reduced the quantum confined stark effect in the AlGaN MQWs.