A way to control the dispersion law is suggested for an interface plasmon polariton propagating in a polariton-active metal-semiconductor structure with a Schottky barrier. An electrical voltage applied across the structure leads to a change in the thickness of the depleted 'insulator' layer at the interface and, as a result, to a change in the polariton dispersion law. Similar considerations are applicable to heterojunctions and metal-insulator-semiconductor structures. It is shown that a low-persistence effective modulator, which is tunable over a wide frequency range, or a controlled reflector, can be constructed on the basis of this effect. Some other possible applications are also discussed, namely light-wave filters, space light modulators, optical spectroscopy of contact potential difference, etc.