Tuning Performance Parameters of Ge-on-Si Avalanche Photodetector-Part II: Large Bias Operation

• Published in: IEEE access Vol. 12; pp. 119238 - 119245
• Main Authors: Chen, Yanning, Liu, Fang, Shao, Yali, Liang, Yingzong, Du, Sichao, Yin, Wen-Yan
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Avalanche diodes; Avalanche photodetector (APD); Avalanche photodiodes; Charge density; Charge materials; Current carriers; Current measurement; Dark current; Electric fields; Figure of merit; Geiger-mode; Germanium; Ionization; Kinetic energy; Lighting; linear multiplication; Parameters; Performance enhancement; Photometers; Silicon; Threshold voltage; vertical Ge-on-Si APD
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2024.3449098

The carrier multiplication phenomenon involves hot carriers, which gain kinetic energy while accelerating to equilibrium with the established avalanching electric fields, and is typically explained via the local avalanche model. This work presents two vertical Ge-on-Si avalanche photodetectors fabricated in a separate absorption, charge, and multiplication configuration. Uniformity in materials, doping densities, and device dimensions is maintained, except for the multiplication width, which is used as a control parameter to manipulate avalanching fields under identical electric biasing and illumination schemes. Nonlocal carrier multiplication model is implemented during analysis of the extracted current-voltage signatures under small and large reverse biasing arrangements. For such an APD characterized by thinner multiplication region <inline-formula> <tex-math notation="LaTeX">\left ({{W_{m}=0.1 ~\mu m}}\right) </tex-math></inline-formula>, reduced linear and Geiger-mode multiplication regimes are perceived to be at play, outperforming the device having thicker multiplication region in almost all related figures of merit, e.g., responsivity <inline-formula> <tex-math notation="LaTeX">(22.58 \mathrm {A/W}) </tex-math></inline-formula>, photo-to-dark current ratio <inline-formula> <tex-math notation="LaTeX">(\sim {10}^{5}) </tex-math></inline-formula>, normalized photo-to-dark current ratio <inline-formula> <tex-math notation="LaTeX">(2.5\times {10}^{9} \mathrm {W}^{-1}) </tex-math></inline-formula>, specific detectivity <inline-formula> <tex-math notation="LaTeX">(7.45\times {10}^{12}\mathrm {Jones}) </tex-math></inline-formula>, and noise equivalent power <inline-formula> <tex-math notation="LaTeX">(\sim 2.42\times {10}^{-15} \mathrm {W/}\sqrt {\mathrm {Hz}}) </tex-math></inline-formula>. The enhanced performance characteristics are due to excessively strong avalanching fields, reduced thermal charge density, and negligible dead space compared to its counterpart characterized by thicker multiplication width.