Theory of Zener-phonon resonances in the transport of two-band semiconductor superlattices

The influence of electron-phonon scattering on intersubband tunnelling in t wo-band semiconductor superlattices is treated on the basis of the density- matrix approach. Intracollisional field effects are accounted for. Three di fferent types of current resonance are identified: (i) electrophonon resona nces, which are expected to appear when a multiple of the Bloch frequency O mega matches the frequency of polar-optical phonons omega (0), (ii) intersu bband tunnelling resonances, and (iii) Zener-phonon resonances, which depen d non-analytically on the electric field strength. The latter resonances ar e most pronounced when the widths of the upper and lower miniband differ ap preciably.