Abstract
We determine the output impedance of uni-travelling carrier (UTC) photodiodes at frequencies up to 400 GHz by performing, for the first time, 3D full-wave modelling of detailed UTC photodiode structures. In addition, we demonstrate the importance of the UTC impedance evaluation, by using it in the prediction of the absolute power radiated by an antenna integrated UTC, over a broad frequency range and confirming the predictions by experimental measurements up to 185 GHz. This is done by means of 3D full-wave modelling and is only possible since the source (UTC) to antenna impedance match is properly taken into account. We also show that, when the UTC-to-antenna coupling efficiency is modelled using the classical junction-capacitance/series-resistance concept, calculated and measured levels of absolute radiated power are in substantial disagreement, and the maximum radiated power is overestimated by a factor of almost 7 dB. The ability to calculate the absolute emitted power correctly enables the radiated power to be maximised through optimisation of the UTC-to-antenna impedance match.
Highlights
Photonic THz emitters based on antennas integrated with uni-travelling carrier photodiodes (UTC-PDs) [1,2,3,4,5,6,7,8,9], are promising candidates for the realisation of sources within the lower part of the THz spectrum (100 GHz – 3 THz) [10,11,12]
In this paper we extend the knowledge of UTC impedance and photo-response up to 400 GHz, by performing for the first time 3D full-wave modelling of the detailed UTC-PD structure, including all epitaxial layers
In the more recent context of photonic THz emitters based on antenna integrated photodiodes, this aspect has so far received little attention
Summary
Photonic THz emitters based on antennas integrated with uni-travelling carrier photodiodes (UTC-PDs) [1,2,3,4,5,6,7,8,9], are promising candidates for the realisation of sources within the lower part of the THz spectrum (100 GHz – 3 THz) [10,11,12]. We showed in [13] that quantum mechanical effects governing the electron transport from the absorber to the collection layer, through the spacers, can affect the conduction properties in a way that, at a macroscopic scale, is reflected in changes in bulk material properties, such as resistivity and electrical permittivity For these reasons, we employ the results of our previous work [13] which will help us assess and refine the material physical properties to employ in the full-wave modelling and simulation, which in turn enables the S11 and the UTC impedance to be evaluated up to frequencies not attainable by measuring equipment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
