The Importance of Schottky Barrier Height in Plasmonically Enhanced Hot-Electron Devices

Abstract

Plasmonically enhanced hot-electron (PEH) photodiodes are a new class of optoelectronic device with the potential to be selective to spectral position, polarization, and bandwidth. Reported solid-state PEH devices based on metal nanoparticles generally have low performance, in part, due to low collection efficiency of photogenerated hot electrons. A correlation is found between the measured external quantum efficiency (EQE) and the temperature at which the ALD-TiO2 is deposited by atomic layer deposition (ALD) in Au–TiO2-based PEH photodiodes. By investigating the material properties of the TiO2, it is demonstrated that the change in EQE is driven by a change in the energy levels in the semiconductor. The results show that lowering the implied Schottky barrier height increases the collection efficiency of hot electrons over the junction, in agreement with existing analytical models. This work demonstrates the crucial role that barrier height plays in hot electron devices in general, and indicates that this is an important design consideration for the improvement of PEH photodetectors.