Aug 15, 2016
Understanding the photosensitivity of resonant tunneling diode photodetectors
Resonant tunneling diodes (RTDs) have active regions of only about 10 nm and are currently the fastest semiconductor devices with fundamental oscillator frequencies up to the THz region. In addition, the small active region further allows to employ RTDs as photosensors with ultra-high sensitivities, the aptitude to detect single photons and even photon counting. Reporting on recent work in Nanotechnology, Fabian Hartmann, postdoctoral researcher and group leader of the Nanoelectronics group at the chair of Technische Physik, Julius-Maximilians-Universität Würzburg explains, "Although it is known that the photosensitivity of RTDs originates from Coulomb interaction of photogenerated and accumulated charge carriers in the vicinity of the resonant tunneling structure, the physical parameters and dependencies that define the RTD photosensitivity are still unexplored."
Three-dimensional sketch of the RTD photodetector and conduction) and valence band profile for an applied bias voltage
In their research paper, the group examine these physical parameters and investigate their dependence on illumination power in detail. For this purpose, they study RTD photodetectors based on a GaAs/AlGaAs double barrier structure with a nearby quaternary GaInNAs light absorbing region, capable of light sensing at the telecommunication wavelength of 1.3 μm at room temperature. They observe that the sensitivity is constant for weak illumination powers, with a photocurrent sensitivity of SI=5.82×103 A/W, which corresponds to a multiplication factor of 330 000. For high illumination powers, the sensitivity decreases by several orders of magnitude. This non-constant sensitivity is attributed to a reduction of the mean lifetime τ of photogenerated holes with increasing hole-population in the vicinity of the resonant tunneling structure.
"Based on these findings, we provide a basic model of the sensitivity, which sets the elementary groundwork for a complete characterization of RTD photodetectors.", says Andreas Pfenning, PhD student at the Nanoelectronics group. "Our results can be applied, and if needed, adjusted to any RTD photosensor. Additionally, they can be used to identify the critical illumination power up to which the RTD photodetector can be operated with constant sensitivity."
More information about this research can be found in the journal Nanotechnology 27 355202.
About the author
Andreas Pfenning received his BS and MS degrees in Nanostructure Technology from Julius-Maximilians-Universität Würzburg (JMU) in 2010 and 2012, respectively. He is currently a PhD student in the "Nanoelectronics" group at the Chair of Technische Physik at JMU. His research interests are within the area of optoelectronic transport properties of resonant tunneling diodes and their application in light sensing.