Abstract: The various embodiments of the present invention provide improved methods and circuits for generating millimeter-wave oscillations. Generating millimeter-wave oscillations may involve providing a semiconductor device comprising at least two terminals and a polar heterojunction formed from two semiconductor materials. A voltage bias may be applied to at least two terminals of the device in which the voltage enhances a two-dimensional electron gas (2DEG) layer at the polar heterojunction and produces a sharply-peaked but spatially-localized electric field within the 2DEG with a large longitudinal component, wherein the longitudinal component of the electric field serves as a nucleation site for a plurality of propagating dipole domains observable as a plurality of self-sustaining millimeter-wave oscillations.

Abstract: An exemplary embodiment of the present invention provides a heterojunction bipolar transistor comprising an emitter, a collector, and a base. The base can be disposed substantially between the emitter and collector. The base can comprise a plurality of alternating type-I and type-II layers arranged to form a short period super lattice. The type-I layers can have a band-gap that is narrower than the band-gap of the type-II layers. At least one of the type-I layers and the type-II layers can consist essentially of a quaternary material.

Abstract: An exemplary embodiment of the present invention provides a heterojunction bipolar transistor comprising an emitter, a collector, and a base. The base can be disposed substantially between the emitter and collector. The base can comprise a plurality of alternating type-I and type-II layers arranged to form a short period super lattice. The type-I layers can have a band-gap that is narrower than the band-gap of the type-II layers. At least one of the type-I layers and the type-II layers can consist essentially of a quaternary material.

Abstract: The various embodiments of the present invention provide improved methods and circuits for generating millimeter-wave oscillations. Generating millimeter-wave oscillations may involve providing a semiconductor device comprising at least two terminals and a polar heterojunction formed from two semiconductor materials. A voltage bias may be applied to at least two terminals of the device in which the voltage enhances a two-dimensional electron gas (2DEG) layer at the polar heterojunction and produces a sharply-peaked but spatially-localized electric field within the 2DEG with a large longitudinal component, wherein the longitudinal component of the electric field serves as a nucleation site for a plurality of propagating dipole domains observable as a plurality of self-sustaining millimeter-wave oscillations.

Abstract: An InGaAs/InAlAs-based avalanche photodetector provides high gain and high bandwidth over a range of operating biases. A graded transition region alleviates the barrier to electron transport from the absorption region to the multiplication region when an operating bias is applied. The graded transition region is a graded bandgap material with a relatively wide bandwidth in the region closer to the multiplication region and a relatively narrow bandgap in the region closer to the absorption region. In another embodiment, a p-type dopant profile is introduced within the absorption layer to produce an electrostatic field which accelerates electrons towards the multiplication region. In another embodiment, a bi-level multiplication region with a wide bandgap ternary layer and a narrower bandgap quarternary layer is provided at an increased thickness to improve gain per unit length.