Thermionic graphene/silicon Schottky infrared photodetectors

Abstract

<p>Optical communications, imaging, and biomedicine require efficient detection of infrared radiation. Growing<br> demand pushes for the integration of such detectors on chips. It is a challenge for conventional semiconductor<br> devices to meet these specs due to spectral limitations arising from their finite band gap, as well as material<br> incompatibilities. Single layer graphene (SLG) is compatible with complementary metal-oxide-semiconductor<br> (CMOS) Si technology, while its broadband (UV to THz) absorption makes the SLG/Si junction a promising<br> platform for photodetection. Here we model the thermionic operation of SLG/Si Schottky photodetectors, considering<br> SLG’s absorption, heat capacity, and carrier cooling dependence on temperature and carrier density. We<br> self-consistently solve coupled rate equations involving electronic and lattice temperatures, and nonequilibrium<br> carrier density under light illumination. We use as an example the infrared photon energy of 0.4 eV, below the<br> threshold for direct photoemission over the Schottky barrier, to study the photothermionic response as a function<br> of voltage bias, input power, pulse width, electronic injection, and relaxation rates. We find that device and<br> operation parameters can be optimized to reach responsivities competitive with the state of the art for any light<br> frequency, unlike conventional semiconductor-based devices. Our results prove that the SLG/Si junction is a<br> broadband photodetection platform.</p>