Lately I have been investigating the physics literature on proposed photosensitive electronic devices made of graphene. Often I see responsivity values quoted as if they suppossed to impress, and there are even comparisons (e.g., "my 10 A/W detector is better than your 1 A/W detector"). An example (picked at random from a google search) is the abstract of this paper.
What I find strange is that responsivity seems, to me, to be completely arbitrary:
- In photoconductive-mode detectors, responsivity depends entirely on the applied voltage bias.
- Responsivity is often dependent on the device size.
- By combining a photodetector with an amplifier, I can make any responsivity as desired.
- Even if we are worried about detecting small currents, this also depends hugely on the impedance of the photodetector. Photodiode amplifiers for example can exploit the high impedance of the signal to amplify very tiny currents.
Am I misunderstanding something here? It seems like responsivity is basically meaningless, and so any claim of "high responsivity" is just pure fluff. Wouldn't a classic metric such as detectivity (comparing to noise level) make a far better figure of merit?