An imaging device may include single-photon avalanche diodes (SPADs). To improve the sensitivity and signal-to-noise ratio of the SPADs, photon detection efficiency (PDE) may be increased. However increased photon detection efficiency may result in a decreased saturation rate and lower than desired dynamic range. To increase the dynamic range, a SPAD-based semiconductor device may operate with multiple sub-exposures. During the first sub-exposure, an over-bias voltage may be set to a first voltage level so that the SPADs have a first photon detection efficiency. During the second sub-exposure, the over-bias voltage may be set to a second voltage level so that the SPADs have a second photon detection efficiency that is different than the first photon detection efficiency. Image data from the first and second sub-exposures may then be combined into a single high dynamic range depth map.