Single-photon avalanche diode (SPAD) based sensors and systems enable a variety of applications in biomedical, automotive, consumer, and security domains. While several established standard technologies, which can facilitate the design of SPAD-based systems are already in existence, challenges remain for the development of deep sub-micron monolithic integration of circuits and SPADs. In this work, we present SPADs along with pixel circuits in a standard GF 55 nm BCDL process. Two different designs demonstrate the flexibility allowed by the technology for a variety of applications. Both shallow and deep junction SPADs present excellent noise performance of less than 1 cps/mu m(2) at 3 V excess bias. An integrated passive-quench active-recharge (PQAR) circuit is used in conjunction with the SPADs, which enables a dead time of less than 2 ns, easily allowing for high dynamic range applications that require > 100 Mcps such as quantum communication and information technologies. The deep and shallow junction SPADs demonstrate an afterpulsing probability of < 0.5 % and < 2 % at 3V excess bias, respectively. The dead time is adjustable through analog control of the active-recharge circuit, allowing for afterpulsing reduction to below 0.1 % while maintaining Mcps operation. The shallow junction, which has a breakdown voltage of about 18 V and a peak sensitivity at 430 nm is particularly interesting for applications requiring low supply voltage, whereas the deep SPAD, which demonstrates > 4 % photon detection probability (PDP) at 940 nm, can be implemented in LiDAR sensors that require enhanced sensitivity at near-infrared (NIR) wavelengths. The measured timing jitter of both SPADs is < 50 ps FWHM at 3 V excess bias and 780 nm.