Pitfalls in Determining the Electrical Bandwidth of Nonideal Nanomaterials for Photodetection

Abstract

The electrical 3 dB bandwidth is regularly used as a measure for the response speed of a photodetector and is estimated via various approaches in literature, ranging from direct measurements to gauged values via approximations. Great care must be taken when comparing these 3 dB bandwidths, since approximations are only strictly valid for ideal circuits. This paper demonstrates that, for typical photodetectors based on new emerging nanostructured materials, namely quantum dots and transition metal dichalcogenides, the bandwidth can deviate up to 10 3 depending on the chosen approach for the bandwidth specification.

A simple 230 MHz photodetector based on exfoliated WSe2 multilayers

“…After conversion to the dB scale, via dB = 10 log 10 ((P(ω))/P 1 ) with the steady state power P 1 , 3 dB bandwidth, i.e., the frequency at which the power drops to half its value, can be read out. 40 Comparing two values for unfocussed and focussed measurements again reflects the factor 23, showing the dependence on the photoresistance and supports the hypothesis of RC-limitation. The non-normalised square pulse measurements can be seen in Fig.…”

A simple 230 MHz Photodetector Based on Exfoliated WSe2 Multilayers

“…License: CC BY 4.0 dB = 10𝑙𝑜𝑔 10 (𝑃(𝜔) 𝑃 1 ⁄ ) with the steady state power 𝑃 1 , the 3 dB bandwidth, i.e., the frequency, at which the power has fallen to half its value, can be read out. 39 Comparing the two values for the unfocussed and focussed measurement again reflects the factor 23, the dependence on the photoresistance, and supports the hypothesis of RC-limitation. The non-normalised square pulse measurements can be seen in Fig.…”

Toward Gigahertz Photodetection with Transition Metal Dichalcogenides

“…Via the power spectrum, the 3 dB bandwidth can be determined, giving the maximal operation frequency at which the initial photocurrent has dropped to 70% . The often-used approximation t rise = 0.35/ f 3 dB can lead to large deviations compared to the much more precise power spectrum, when calculating the bandwidth A1 Top panels show the laser power applied.…”