High Responsivity and Detectivity Graphene-Silicon Majority Carrier Tunneling Photodiodes with a Thin Native Oxide Layer

A photocurrent amplifier operable at low bias voltages with high responsivity and detectivity is highly demanding for various optoelectronic applications. This study shows majority carrier graphene-native oxide-silicon (GOS) photocurrent amplifiers complying with the demands. The photocurrent amplification is primarily attributed to the photoinduced Schottky barrier height (SBH) lowering for majority carriers. The unavoidably formed thin native oxide layer between graphene and silicon during the wet graphene transfer process plays significant roles in lowering of the dark leakage current as well as photoinduced SBH lowering. As a result, the photocurrent to dark current ratio is as high as ∼12.7 at the optical power density of 1.45 mW cm^–2. These GOS devices show a high responsivity of 5.5 AW^–1 at an optical power (458 nm in wavelength) of 15 μWcm^–2, which corresponds to ∼1400% quantum efficiency. Further the response speed is as fast as a few ten-microseconds. Thus, these GOS majority carrier photodiodes show the highest detectivity (2.35 × 10¹⁰ cm Hz^1/2 W^1–) among previously reported graphene-silicon photodiodes. However, the responsivity decreases with the optical power density due to the increasing recombination rate through the interface states proportional to the optical power density.