Theory of Zener tunneling and Wannier-Stark states in semiconductors

A general multiband and multichannel scattering theory of the current in mesoscopic-device structures is developed and applied to the Zener diode. It takes into account the realistic electronic structure, its modification by the high electric field, and the field-free contact regions in a nonperturbative manner. This theory elucidates the interplay between Zener tunneling and Wannier-Stark resonances. Quantitative conditions for the occurrence of Wannier-Stark oscillations in the current of a bulk semiconductor or superlattice are derived. It is predicted that Wannier-Stark resonances are detectable in the interband tunneling current of highly doped submicrometer p-i-n diodes with very short i zones. We show that there are two regimes in the Zener tunneling current: a low-field or Zener regime where the conductance is a smooth function of the applied voltage, and a high-field or Stark regime where Wannier-Stark resonances are induced.