Deep UV-LEDs with high IQE based on AlGaN alloys with strong band structure potential fluctuations

Abstract

In this paper we review our progress in developing AlGaN-based deep UV LEDs with internal quantum efficiency (IQE) in excess of 50%. This is accomplished by growing the active region of the LEDs by plasma-assisted MBE under a growth mode which promotes the introduction of deep band structure potential fluctuations in the wells beyond the statistical ones due alloy disorder. AlGaN-based deep UV-LEDs emitting in the wavelength range from 320 nm to 265 were grown by this method and fabricated into devices. By combining high IQE AlGaN QWs in the active region with polarization field enhanced carrier injection layers, unpackaged deep UV-LEDs emitting at 295 nm and 273 nm were obtained with optical output power of 0.35 mW and 1.8 mW at 20 mA continuous wave and 100 mA pulsed drive current, respectively. The maximum external quantum efficiency of these devices was calculated to be 0.4%, a result consistent with the low extraction efficiency of only 1-2%.