An IR photodetector including an IR semiconductor detector with conductive layers on opposite, parallel surfaces. A semiconductor substrate supports the semiconductor IR detector. A circuit is connected across the semiconductor IR detector to provide a bias voltage and for measuring current flow through the semiconductor IR detector. The semiconductor IR detector has a lattice structure made up of a series of potential wells separated by relatively wide potential barriers such that each well has two confined energy levels. A thin spike barrier is placed in the center of alternate potential wells to tailor the absorption characteristics of the semiconductor IR detector. Multicolor operation is achieved by selecting the appropriate well widths for a first group of potential wells and by placing thin spike barriers in a second group of potential wells that are alternately placed between the wells of the first group.