Enhanced Luminescence of InGaN-Based 395nm Flip-Chip Near-Ultraviolet Light-Emitting Diodes with Al as N-Electrode
Jin Xu, Wei Zhang, Meng Peng, Jiang-Nan Dai**, Chang-Qing Chen
Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074
Abstract：High-reflectivity Al-based n-electrode is used to enhance the luminescence properties of InGaN-based 395 nm flip-chip near-ultraviolet (UV) light-emitting diodes. The Al-only metal layer could form the Ohmic contact on the plasma etched n-GaN by means of chemical pre-treatment, with the lowest specific contact resistance of $2.211\times10^{-5}$ $\Omega\cdot$cm$^{2}$. The Al n-electrodes enhance light output power of the 395 nm flip-chip near-UV light-emitting diodes by more than 33% compared with the Ti/Al n-electrodes. Meanwhile, the electrical characteristics of these chips with two types of n-electrodes do not show any significant discrepancy. The near-field light distribution measurement of packaged chips confirms that the enhanced luminescence is ascribed to the high reflectivity of the Al electrodes in the UV region. After the accelerated aging test for over 1000 h, the luminous degradation of the packaged chips with Al n-electrodes is less than 3%, which proves the reliability of these chips with the Al-based electrodes. Our approach shows a simplified design and fabrication of high-reflectivity n-electrode for flip-chip near-UV light emitting diodes.
2017, Vol. 34 
