Abstract
Ohmic contacts were formed by varying the Ti/Al thickness ratios in the Ti/Al/Ni/Au metal stack. Based on the Ti/Al/Ni/Au metal electrode in n-AlGaN, several deep ultraviolet light emitting diode (DUV LED) chips were fabricated. Annealed at different temperatures, the different structures and ohmic contacts in these Ti/Al/Ni/Au electrodes were correlated by X-ray diffraction (XRD) pattern, scanning electron microscope (SEM) and atomic force microscope (AFM). The XRD results show that the TiN and AlTi3 phases were formed after two-step high-temperature annealing process. The influence of ohmic contact on the Ti/Al/Ni/Au metal stack on the n-AlGaN performance was explored by optimizing the Ti thickness of contact layer. It demonstrated that when the Ti/Al thickness ratio is 5.41 (Ti = 35 nm), the ohmic contact on Ti/Al/Ni/Au metal stack exhibited the lowest specific contact resistance which is about 3.21x10-5 (Ω·cm2). The I-V curve and I-L curve results of the DUV LED devices fabricated by Ti/Al/Ni/Au metal stacks demonstrate the ohmic contact performance. These results indicated the ohmic contact formation by varying Ti/Al thickness ratios on the Ti/Al/Ni/Au metal electrode is favorable to the application in the n-AlGaN-based DUV LED.
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