  Recent advances in guiding and localizing light at the nanoscale exposed the
enormous potential of ultra-scaled plasmonic devices. In this context, the
decay of surface plasmons to hot carriers triggers a variety of applications in
boosting the efficiency of energy-harvesting, photo-catalysis and
photo-detection. However, a detailed understanding of plasmonic hot carrier
generation and particularly the transfer at metal-semiconductor interfaces is
still elusive. In this paper, we introduce a monolithic metal-semiconductor
(Al-Ge) heterostructure device, providing a platform to examine surface plasmon
decay and hot electron transfer at an atomically sharp Schottky nanojunction.
The gated metal-semiconductor heterojunction device features electrostatic
control of the Schottky barrier height at the Al-Ge interface, enabling hot
electron filtering. The ability of momentum matching and to control the energy
distribution of plasmon-driven hot electron injection is demonstrated by
controlling the interband electron transfer in Ge leading to negative
differential resistance.
