Tuning the Plasmonic Resonance Peak for Al Nanorods on AlGaN Layer to Deep Ultraviolet Band

Tuning the plasmonic resonance peak to the deep ultraviolet (DUV) band is critical for plasmonic-enhanced AlGaN-based DUV photodetector. However,the high refractive index of AlGaN layer seriously limits the plasmonic resonance peak in DUV band. Therefore, in this work, we study how various Al nanoparticles on the AlGaN layer surface affect the plasmonic resonance performance. Compared with the Al-based nanosphere, nanohemisphere and nanodisk, the Al-based nanorod is the most suitable candidate for AlGaN-based DUV photodetectors. This is because the DUV plasmonic dipolar mode excited from the upper part of nanorod is not affected by the interface between the nanorods and the AlGaN layer. However, the interface also leads to another plasmonic dipolar mode at longer wavelengths. Moreover, the DUV plasmonic resonance peak will be influenced by the diameter, the height and the Al
₂
O
₃
layer thickness. We also find that the diffraction can enhance the resonance peak intensity when the Al nanorod period is smaller than the resonance peak wavelength. Besides, to make the enhanced electric field located in active layer, a layer of Ga
₂
O
₃
shell is proposed to cover Al nanorods, which causes a quadrupole mode in DUV band excited from the sidewall of Al nanorods.