Highly improved performance of a 350 nm ultraviolet light-emitting diode containing Al xGa 1− xN/Al yGa 1− yN distributed Bragg reflectors

Abstract

By introducing Al 0.49Ga 0.51N/Al 0.16Ga 0.84N distributed Bragg reflectors (DBRs), the performance of an ultraviolet (UV) light–emitting diode (LED) with an emission wavelength of about 350 nm on a sapphire substrate was dramatically improved. The output power was enhanced by a factor of 2.3, compared to the conventional UV-LED with a similar emission wavelength. This enhancement due to the DBRs was larger than that occurring in InGaN-based blue LEDs also containing DBRs, in which the increase of optical power with a factor of 1.5 was reported compared to the InGaN-based blue LEDs without DBRs. This can be attributed to the introduction of DBRs into the UV-LED which can strongly suppress the so-called internal absorption issue, one of the key factors impeding the performance of UV-LEDs grown on sapphire substrates with emission wavelengths below 362 nm, the GaN bandgap.