Strain engineering for enhanced hot-carrier photodetection

Abstract

Hot-carrier devices in metal–semiconductor junctions have attracted considerable attention but still with quantum efficiencies far from expectations. Introducing the lattice strain to the material can effectively modulate the electronic structure, providing a way to control the hot-carrier dynamics. Here, we study how this strain affects the generation, transport, and injection of hot carriers in gold (Au) by using first-principles calculations and evaluate the overall responses of Au-based hot-carrier devices by Monte Carlo simulation. We find that the compressive strain can significantly increase the hot-electron generation from direct transition at E > 1.1 eV for Au. The compressive strain delocalizes the band structure and decreases the electron density of state, which, in turn, reduce electron–electron and electron–phonon scatterings to improve the transport of hot carriers. Taking the Au/TiO2 device as an example, we find that the compressive strain (−6%) can enable a 1.5- to 3-fold enhancement of quantum efficiency and responsivity at a photon energy between 1.2 and 3 eV.