Uni-Traveling-Carrier Photodetector With High-Reflectivity DBR Mirrors

A novel uni-traveling-carrier photodetector (UTC-PD), bonded to high-reflectivity (HR) distributed Bragg reflector (DBR) mirrors, referred to as HR-UTC-PD, is first developed to overcome the bandwidth-responsivity tradeoff in UTC-PDs at various wavelengths. Grubbs' test is adopted, for the first time, to measure the bonded thickness of random locations for evaluating the reflected light loss generated in the bonded region. Compared with a standard UTC-PD without HR DBR mirrors, the maximum improvement of HR-UTC-PD responsivity (0.88A/W at 1560 nm) is 24.4% under a bias voltage of 3 V. The obtained 3-dB bandwidth for a 40-μm-diameter PD, which is neither increased nor degraded with the HR DBR mirrors, is 13.87 GHz at a bias voltage of 6 V and a 1550 nm wavelength. The saturation current up to 50 mA at 1-dB compression point is obtained at the frequency of 10 GHz, under a 50-Ω load and a 6 V bias voltage.