Sett, Shaili and Raychaudhuri, A K (2020) Effective Separation of Photogenerated Electron-Hole Pairs by Radial Field Facilitates Ultrahigh Photoresponse in Single Semiconductor Nanowire Photodetectors. Journal of Physical Chemistry C, 124 (41). pp. 22808-22816. ISSN 1932-7447

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We report an investigation on the observation of ultrahigh photoresponse (photogain, G(Pc) > 10(6)) in single nanowire photodetectors of diameter <100 nm. The investigation, which is a combination of experimental observations and theoretical analysis of the ultrahigh optical response of semiconductor nanowires, has been carried out with an emphasis on Ge nanowires. Semiconductor nanowire photodetectors show a signature of photogating where G(Pc) rolls off with increasing illumination intensity. We show that surface band bending due to depleted surface layers in nanowires induces a strong radial field (similar to 10(8 )V/m at the nanowire surface) that causes physical separation of photogenerated electron-hole pairs. This was established quantitatively through a self-consistent theoretical model based on coupled Schrodinger and Poisson equations. It shows that carrier separation slows down the surface recombination velocity to a low value (<1 cm/s), thus reducing the carrier recombination rate and extending the recombination lifetime by a few orders of magnitude. An important outcome of the model is the prediction of G(Pc) similar to 10(6) in a single Ge nanowire (with diameter 60 nm), which matches well with our experimental observation. The model also shows an inverse dependence of G(Pc) on the diameter that has been observed experimentally. Though carried out in the context of Ge nanowires, the physical model developed has general applicability in other semiconductor nanowires as well.

Item Type: Article
Subjects: Electronics
Depositing User: Bidhan Chaudhuri
Date Deposited: 25 Jan 2021 10:57
Last Modified: 25 Jan 2021 10:57

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