Methods, devices, apparatus, and systems for photo-detecting are provided. The photo-detecting apparatus includes a substrate, an absorption region supported by the substrate and configured to receive an optical signal and generate photo-carriers in response to the optical signal, and multiple sets of a switch including a first set and a second set. The substrate includes a first material, and the absorption region includes a second material. The absorption region is arranged in between the first set and the second set. Each of the multiple sets includes a respective control region and a respective readout region. The respective control regions of the multiple sets of the switch are configured to receive a control signal, and the respective readout regions of the multiple sets of the switch are configured to provide one or more electrical signals representing first collective information for deriving time-of-flight information associated with the optical signal.