Theory of high-field-domain structures in superlattices

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Abstract
A number of experimental works provide evidence for the existence of high-field domains in superlattices when the applied voltage exceeds some critical value. A theoretical description of the structure of such a domain is developed. We confine ourselves to the case of narrow-band superlattices, where electrons are strongly localized in the wells. We find that the minimum length of the high-field domain can be larger than one superlattice period. The maximum current in the oscillating part of the I-V characteristic can be significantly smaller than the value of the current at the voltage where the first instability comes aobut. The oscillation period can be considerably smaller than the value corresponding to the energy separation between the first and the second level in a well. For the case of the domain formation at some distance from the anode, we study the field distribution in the low-field region downstream of the domain.