Semiconductor nanostructures, such as quantum wells and quantum dots (QD), are well known, and some have been
incorporated in applications. Here will focus on novel structures made of QDs and related devices for terahertz (THz)
generation. Their potential advantages, such as low threshold current density, high characteristic temperature, increased
differential gain, etc., make QDs promising candidates for light emitting applications in the THz region. Our idea of
using resonant tunneling through QDs is presented, and initial results on devices consisting of self assembled InAs QDs
in an undoped GaAs matrix, with a design incorporating GaInNAs/GaAs short period superlattice, are discussed.
Moreover, shallow impurities are also being explored for possible THz emission: the idea is based on the tunneling
through bound states of individual donor or acceptor impurities in the quantum well. Initial results on devices having an
AlGaAs/GaAs double barrier resonant tunneling structure are discussed.