Abstract
We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances. Compared with the conventional grating design, the multi-layered grating system under conformal configuration is demonstrated to possess both optical and electrical advantages for high-sensitivity hot-electron photodetection. Finite-element simulation reveals that a strong and highly asymmetrical optical absorption (top metal absorption >99%) can be realized under such a conformal arrangement. An analytical probability-based electrical simulation verifies the strong unidirectional photocurrent, by taking advantage of the extremely high net absorption and a low metal/semiconductor barrier height, and predicts that the corresponding photoresponsivity can be ~3 times of that based on the conventional grating design in metal-insulator-metal (MIM) configuration.
Highlights
We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances
Photodetection and photovoltaic conversion based on plasmonic hot electrons have been widely discussed in recent years[17,18,19,20,21,22,23,24]
We design a plasmonic hot-electron photodetection system under conformal metalsemiconductor-metal (MSM) grating configuration, which is a modified MIM structure and shows no qualitative difference in underlying operation principles with those reported in Refs 18,21 since doping is not needed for the proposed device
Summary
A thin Ti adhesion layer is deposited by electron-beam evaporator on a quartz substrate [Fig. 6(a)]. A thick Au film is evaporated onto the adhesion layer [(Fig. 6(b)]. Electron beam resist is spin-coated and exposed by electron beam lithography technology [(Fig. 6(c,d)]. 1-D aligned stripes are obtained after lifting-off the exposed resist [(Fig. 6(e)]. Ar ion beam is employed to etch the resist-patterned sample, and the patterns can be copied to the Au film after removing the residual resist [(Fig. 6(f,g)]. 4-nm-thick ZnO film and a thin Au film are deposited in sequence by atomic layer deposition (ALD) in order to guarantee the good conformal morphologies [(Fig. 6(h,i)]. Two electrodes/probes contacting separately the top and bottom Au films are created to enable current-voltage measurements
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