We have made a detailed study of the effects of photon radiation in the energy range between 0.5 and 5.0 eV on InSb metal‐oxide‐semiconductor (MOS) devices. Measurements of the photocurrent through the MOS structures made at several temperatures showed that even at 300°K a photovoltage is developed for photon energies greater than about 1.3 eV. For photon energies above 3 eV the indium‐antimony oxide layer became photoconductive. The charging and discharging characteristics of the InSb‐oxide interface were investigated by measuring the response of the InSb&sngbnd;MOS structure to modulated long wavelength (3.9 &mgr;) radiation. This radiation acts as a probe for examining the band bending in the InSb at the InSb‐oxide interface, which in turn depends on the amount of charge trapped in the oxide or at the interface. When the MOS structure is irradiated with 1.3‐ to 4‐eV photons, the oxide and/or the interface becomes negatively charged. At photon energies above 3.5 eV there is a competition between the mechanism which induces negative charge in the oxide and/or interface region and the mechanism which releases this charge. This competition can be influenced by applied bias, and by properly biasing the device and irradiating with photons having energies greater than 4 eV the charges can be released.