Post-removal for the deposited Au metal to increase the light extraction efficiency for AlGaN-based deep-ultraviolet
Abstract:
Ni/Au is employed to ensure a high-quality p-type ohmic contact for most AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs). However, the substantial absorptivity of ultraviolet light by Ni/Au significantly impacts the light extraction efficiency (LEE). In this work, to reduce the absorptivity of a Ni/Au electrode, we conduct wet-etching to the Ni/Au electrode after the formation of ohmic contact between Ni/Au and p-AlGaN. Experimental results show that the optical transmittance of the Ni/Au electrode can be improved from 35.2% to 42.68% after the Ni/Au is wet-etched for 5 min. When compared with the reference device, the optical power and the wall plug efficiency (WPE) of the proposed device are enhanced by 10.24% and 9.89% at an injection current of 100 mA, respectively. Although the proposed DUV LED exhibits a 0.30 V increase in forward voltage, this does not affect the device's stability after making a 1000-h lifetime test. This proposed method not only can improve the LEE but also is fully compatible with the mass production of DUV LEDs.
