Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

• Published in: Applied physics letters 2018-02, Vol.112 (7)
• Main Authors: Zhang, Yuewei, Jamal-Eddine, Zane, Akyol, Fatih, Bajaj, Sanyam, Johnson, Jared M., Calderon, Gabriel, Allerman, Andrew A., Moseley, Michael W., Armstrong, Andrew M., Hwang, Jinwoo, Rajan, Siddharth
• Format: Article
• Language: English
• Subjects: Applied physics; Efficiency; Electric contacts; Electromagnetic absorption; Emitters; Light emission; Light emitting diodes; Low resistance; Organic light emitting diodes; Quantum efficiency; Tunnel junctions; Ultraviolet radiation
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5017045

We report on the high efficiency tunnel-injected ultraviolet light emitting diodes (UV LEDs) emitting at 287 nm. Deep UV LED performance has been limited by the severe internal light absorption in the p-type contact layers and low electrical injection efficiency due to poor p-type conduction. In this work, a polarization engineered Al0.65Ga0.35N/In0.2Ga0.8N tunnel junction layer is adopted for non-equilibrium hole injection to replace the conventionally used direct p-type contact. A reverse-graded AlGaN contact layer is further introduced to realize a low resistance contact to the top n-AlGaN layer. This led to the demonstration of a low tunnel junction resistance of 1.9 × 10−3 Ω cm2 obtained at 1 kA/cm2. Light emission at 287 nm with an on-wafer peak external quantum efficiency of 2.8% and a wall-plug efficiency of 1.1% was achieved. The measured power density at 1 kA/cm2 was 54.4 W/cm2, confirming the efficient hole injection through interband tunneling. With the benefits of the minimized internal absorption and efficient hole injection, a tunnel-injected UV LED structure could enable future high efficiency UV emitters.