Adsorbate-induced enhancement of the spectral response in graphene/silicon-based Schottky barrier photodetectors

Abstract

The impact of atmospheric adsorbates on the spectral response and response speed of p-type graphene/n-type Silicon (p-Gr/n-Si) based Schottky barrier photodetectors are investigated. Wavelength resolved photocurrent and transient photocurrent spectroscopy measurements conducted under high-vacuum conditions revealed that the atmospheric adsorbates such as O2 and H2O stuck on graphene electrode lead to hole doping in graphene and therefore shift its Fermi level towards higher energy states below its Dirac point. Such a shift in graphene’s Fermi level due to adsorbates increases the zero-bias Schottky barrier height of the p-Gr/n-Si heterojunction from 0.71 to 0.78 eV. Adsorbate induced increment in the barrier height promotes the separation of photo-generated charge carriers at the depletion region and leads to an improvement in the maximum spectral response (e.g., from 0.39 to 0.46 AW−1) and response speed of the p-Gr/n-Si photodetector in the near-infrared region. The experimentally obtained results are expected to give an insight into the adsorbate related variations in the rectification and photo-response characters of the heterojunctions of graphene and other 2D materials with different semiconductors.