High-Efficiency and High-Reliability Deep-UV Light-Emitting Diodes Using Transparent Ni-Implanted AlN Ohmic Electrodes

Significant efforts have been devoted to improve the external quantum efficiency (EQE) of AlGaN-based top-emitting deep-UV light-emitting diodes (DUV LEDs). However, issues such as ohmic contact and challenges related to p-AlGaN doping and growth have hampered advancement. In this paper, a record-high EQE of 3.2% is reported for AlGaN-based lateral-type top-emitting DUV LEDs in which Ni-doped AlN (Ni:AlN) DUV-transparent ohmic electrodes are used. The ohmic electrode exhibits a transmittance of more than 90% at 280 nm and a reasonably good ohmic behavior with the p-Al
_0.64
Ga
_0.36
N contact layers. The Ni:AlN-based DUV LED demonstrates outstanding performance (i.e., operating voltage of 8.3 V at 20 mA, light output power of 11.6 mW at 100 mA) relative to the conventional thin ITO- and Ni/Au-based DUV LEDs. Furthermore, the proposed device is highly reliable, as evidenced by the fact that it maintained more than 80% of its light output power after 500 h of operation, and the operating voltage increased by only 2.7% over the operating time of 1
$\times \,\,10^{5}\text{s}$
.