Open access
Autor(in)
Datum
2019Typ
- Doctoral Thesis
ETH Bibliographie
yes
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Abstract
Indium phosphide high electron mobility transistors (InP HEMTs) represent
the state-of-the-art technology for both room and cryogenic temperature low
noise amplifiers. For years they have been playing a central role in the most
demanding niche applications such as radio astronomy and deep space communications,
and they are expected to significantly contribute to communication
networks of the future. Modern lithography tools have enabled straightforward
processing of transistors with sub-100nm gate lengths, however, the
improved RF performance did not result in the expected advancement of
noise behavior. The physical limits of noise performance are currently motivating
research into this subject, with indications that a significant decrease
of minimum noise figure from reducing the gate length cannot be expected.
Nevertheless, there is room for improvement in transistor noise behavior with
further development of epitaxial growths and bandgap engineering.
This work centers on the optimization of InP HEMTs epitaxial layers by
bandgap engineering, small-signal modeling and characterization. A common
approach in improving carrier confinement and mobility with narrow
bandgap materials used for the channel results in impact ionization taking
place even at a relatively low drain bias. The small-signal model was
extended to account for the effects of impact ionization and now features
excellent agreement between simulated and measured S-parameters at lower
frequencies at both room and cryogenic temperatures: we are now able to
resolve in which material impact ionization takes place in a composite channel.
The noise model proposed in this work including the impact ionization
effects shows good agreement with noise measurements performed at room
temperature. Achieving the best possible transistor gain and noise behavior
depends highly on the quality of contacts: epitaxial structures were therefore
optimized in order to reduce contact resistance and improve channel
transport properties. Composite channel structures with narrow and wide
bandgap materials were implemented to reduce the effects of impact ionization.
Further refining of the channel layers in combination with vertical
device scaling should allow improvement of both the device bandwidth and
minimum noise figure. Mehr anzeigen
Persistenter Link
https://doi.org/10.3929/ethz-b-000377434Publikationsstatus
publishedExterne Links
Printexemplar via ETH-Bibliothek suchen
Verlag
ETH ZurichOrganisationseinheit
03721 - Bolognesi, Colombo / Bolognesi, Colombo
ETH Bibliographie
yes
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