A solid-state photodetector with variable spectral response that can produce a narrow or wide response spectrum of incident light. Some embodiments include a solid-state device structure that includes a first photodiode and a second photodiode that share a common anode region. Bias voltages applied to the first photodiode and/or the second photodiode may be used to control the thicknesses of depletion regions of the photodiodes and/or a common anode region to vary the spectral response of the photodetector. Thickness of the depletion regions and/or the common anode region may be controlled based on resistance between multiple contacts of the common anode region and/or capacitance of the depletion regions. Embodiments include control circuits and methods for determining spectral characteristics of incident light using the variable spectral response photodetector.