High-Gain N-Face AlGaN Solar-Blind Avalanche Photodiodes Using a Heterostructure as Separate Absorption and Multiplication Regions
Yin Tang1, Qing Cai1, Lian-Hong Yang2, Ke-Xiu Dong3, Dun-Jun Chen1**, Hai Lu1, Rong Zhang1, You-Dou Zheng1
1Key Laboratory of Advanced Photonic and Electronic Materials, School of electronic Science and Engineering, Nanjing University, Nanjing 210093 2Department of Physics, Changji College, Changji 831100 3School of Mechanical and Electronic Engineering, Chuzhou University, Chuzhou 239000
Abstract：It is well known that III-nitride semiconductors can generate the magnitude of MV/cm polarization electric field which is comparable with their ionization electric fields. To take full advantage of the polarization electric field, we design an N-face AlGaN solar-blind avalanche photodiode (APD) with an Al$_{0.45}$Ga$_{0.55}$N/Al$_{0.3}$Ga$_{0.7}$N heterostructure as separate absorption and multiplication (SAM) regions. The simulation results show that the N-face APDs are more beneficial to improving the avalanche gain and reducing the avalanche breakdown voltage compared with the Ga-face APDs due to the effect of the polarization electric field. Furthermore, the Al$_{0.45}$Ga$_{0.55}$N/Al$_{0.3}$Ga$_{0.7}$N heterostructure SAM regions used in APDs instead of homogeneous Al$_{0.45}$Ga$_{0.55}$N SAM structure can increase significantly avalanche gain because of the increased hole ionization coefficient by using the relatively low Al-content AlGaN in the multiplication region. Meanwhile, a quarter-wave AlGaN/AlN distributed Bragg reflector structure at the bottom of the device is designed to remain a solar-blind characteristic of the heterostructure SAM-APDs.
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