Bloch Oscillating Super-Superlattices

Bloch oscillation in electrically biased semiconductor superlattices offers broadband terahertz gain from DC up to the Bloch frequency and can provide a basis for solid-state electronic oscillators operating at 10 times the frequency of existing devices. To circumvent the inherent instability of the electrically biased doped superlattices to the formation of static or dynamic electric field domains, we have fabricated super-superlattices in which a large superlattice is punctuated with heavily doped regions. Room temperature, terahertz photon assisted transport in short InGaAs/InAlAs superlattice cells allows us to determine the Stark ladder splitting as the superlattice is electrically biased and confirms the absence of electric field domains in short structures. Absorption of radiation from 1.5 to 2.5 THz by electrically biased InAs/AlSb super-superlattices exhibit a crossover from loss to gain as the Stark ladder is opened.