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.