An experimental investigation was made on the use of a PtSi Schottky barrier for blocking injected electron dark current in a back‐illuminated impurity‐band‐conduction (IBC) photodetector, a device used for detecting long‐wavelength infrared (LWIR) radiation. Measured results on the Schottky barrier height as well as current versus applied bias results are presented, and show that the desired blocking capability has been attained. At the low operating temperatures (∼10 K) of the IBC device, the injected dark current is below our measurement capability for applied biases of up to 10 V. Injected dark current in conventional devices occurs at biases of ∼1 V. The modified device configuration discussed here would enable one to store the mobile ionized donor charge for subsequent readout. ©1995 American Institute of Physics.