Ultra-thin p-AlGaN insert layer for enhancing the electrical performance of AlGaN-based deep-ultraviolet light-emitting diodes

A composite p-contact structure is proposed to enhance the electrical performance of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs). With the insertion of a 1 nm-thick p-AlGaN layer prior to the contact layer, the operating voltage at 100 mA is significantly reduced by 0.2-0.3 V in 277 nm DUV-LEDs, leading to a maximum wall-plug efficiency of 10.7%. It is experimentally demonstrated that the reduction of operating voltage is mainly attributed to the lower specific contact resistivity of p-contact. The improvement mechanism of contact property is further explored by the theoretical calculations of energy band, where the hole accumulation in the contact layer, owing to the greater valence band offset induced by the p-AlGaN insert one, is speculated to promote the tunneling at the metal/semiconductor interface. The composite p-contact structure in this study is compatible with the present commercial DUV-LED epitaxial structure, enabling it to promote further development of this field.