Linear Mode CMOS Compatible p-n Junction Avalanche Photodiode for Smart-lighting Applications

There is a need in emerging smart lighting concepts for a high-speed sensing capability to enable adaptive lighting (smart spaces) and visible light communication. One approach to address this need is to design and manufacture a novel complementary-metal—oxide—semiconductor (CMOS) compatible, cost-effective detector array and readout circuit (ROIC) that incorporates integrated waveguide detectors and avalanche photodiodes (APDs). This thesis focuses on the APD design and fabrication component of the sensing capability required by smart-lighting systems. Silicon CMOS compatible APDs are expected to provide high-speed and high-sensitivity sensors in terms of simplicity of design, low power consumption and cost-effectiveness for smart-lighting applications. To date, most of the CMOS-based APD devices have been dedicated to the Geiger mode, which aims to count individual photons under ultralow light conditions. This thesis reports on the modeling, design, fabrication,and characterization of CMOS compatible p-n junction Si APDs to be operated in the linear avalanche mode. The recursive dead-space multiplication theory (DSMT), is applied to the recently fabricated thin Si n+p APDs to predict the avalanche and breakdown properties including low excess noise factor. The low excess noise factor is due to the presence of dead space effect and the initiation of avalanche process by the photogenerated electron in the depletion region of Si APDs. The calculated mean gain, avalanche breakdown voltage, excess noise factor, electron and hole ionization coefficients, electric fields are reported. Moreover, measured dark current, photocurrent, mean gain, capacitance, spectral response, and breakdown voltages are also reported supporting low-voltage operation across the visible electromagnetic spectrum. A mean gain of ~50 has been obtained for the fabricated structure at a reverse bias breakdown voltage of ~8.67 V. The type of APD developed in this thesis can be integrated with waveguide structures to provide enhanced sensitivity and high speed detection capability as well as uniformity across colors