Stability of surface-helical waves with low amplitude relative to the modulations

The condition for the stability of helical waves in semiconductor rods and plates relative to modulations is derived. The necessary numerical calculations were performed for the semiconductors Ge, Si, and InSb. The conditions under which selfmodulation of the helical waves can be observed are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 92–97, October, 1987.