Influence of Undoped-AlGaN Final Barrier of MQWs on the Performance of Lateral-Type UVB LEDs

Aluminium gallium nitride (AlGaN)-based ultraviolet-B light-emitting diodes (UVB LEDs) are expected to offer smart size, wider choice of UVB light emission in the wavelengths range of 280 nm > lambda > 320 nm, and low cost as well as low power consumption compared with other UV light sources including toxic mercury UV-lamps. The hole-tunneling from p-AlGaN side of UVB LED into the multi-quantum-wells (MQWs) is strongly dependent on the thickness (T-FB) and Al-contents of undoped (ud)-AlGaN final barrier (FB). Herein, the photoluminescence (PL) efficiency from MQWs of the UVB LED devices is investigated and compared with the electroluminescence (EL) spectra as a function of T-FB. Subsequently, the dependence of PL efficiency, external quantum efficiency (EQE), and light output power on the T-FB of UVB LEDs is attempted, using the same growth condition for all samples except variation in T-FB. When T-FB is set to 6-7 nm, improvements in the EQE and light output power, respectively, from 4.3% and 7 mW to the high values of 5.6% and 17 mW in emission band of 295-300 nm under continuous-wave (cw) at room temperature (RT) are achieved.