High-responsivity and high-output-power MUTC-PD utilizing distributed Bragg reflectors
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Published on: July 18, 2015
Mengjing Xu1, Zixuan Cheng1, Qian Yu1
1Beijing National Research Centre for Information Science and Technology (BNRist), State Key Laboratory of Space Network and Communications, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China.
Abstract:
We demonstrate a weakly resonant cavity-enhanced modified uni-traveling-carrier photodiode (MUTC-PD) incorporating distributed Bragg reflectors (DBRs), enabling enhanced optical absorption through controlled weak resonance while preserving wide bandwidth to overcome the responsivity-bandwidth trade-off in high-speed photodetectors. This absorption enhancement provides additional design freedom to scale the device area, leading to reduced space-charge effects under high optical excitation and enabling higher saturation current and output power. The resonant enhancement is analyzed using the transfer matrix method, while an optimized cliff layer enables electron velocity overshoot and suppresses space-charge screening. The fabricated device achieves a peak responsivity of 0.78 A/W at 1550 nm under -5 V bias, representing a 1.7× improvement over conventional MUTC-PDs. Photodiodes with diameters of 30, 20, and 12 μm exhibit 3-dB bandwidths of 36, 49, and 68 GHz, respectively, and RF output power of 17.3 dBm at 30 GHz, 16.0 dBm at 40 GHz, 7.1 dBm at 60 GHz is demonstrated.
