Infrared Surface Plasmons Open a Hole Tunneling Channel in Metal–Oxide–Semiconductor Structures

Abstract

Plasmonic hot carriers on metal−oxide−semiconductor (MOS) diodes hold the promise of innovative optoelectronics on structures of fundamental technological importance. We report the photoresponse of MOS diodes due to the tunneling of hot holes created in the metal contact via the absorption of infrared (λ 0 ≈ 1550 nm, ℏω ≈ 0.8 eV) surface plasmons therein. In the absence of illumination, only one tunneling channel exists under inversion, that of inversion electrons tunneling from the semiconductor conduction band through the oxide barrier into the metal, leading to the dark current. Under illumination, the excitation and decay of surface plasmons in the metal opens a second channel, that of hot holes created in the metal, tunneling through the oxide into the semiconductor valence band, leading to the photocurrent�this channel does not exist otherwise due to the absence of holes in a metal. Theoretical modeling of all tunneling current components (dark and photo) using the Fowler−Nordheim and Modified Fowler−Nordheim models are in excellent agreement with the measurements, and their fit allows extraction of the tunneling effective masses of both carrier types in the oxide of our MOS structures (hafnia). This new plasmon-induced tunneling channel on MOS structures opens the possibility of novel infrared optoelectronic devices on this technologically important structure..