Epitaxial Graphene/n-Si Photodiode with Ultralow Dark Current and High Responsivity

TL;DR

Researchers created a high-performance photodetector using graphene and silicon, achieving low dark current and high sensitivity for optoelectronics.

Contribution

A novel epitaxial graphene/n-Si heterojunction photodiode with ultralow dark current and high responsivity is demonstrated.

Findings

The photodetector achieves an ultralow dark current of 1.2 × 10−9 A.

It demonstrates a high responsivity of 1430 A/W at room temperature.

The device enables self-powered operation without polymer residues or interface defects.

Abstract

Graphene’s exceptional carrier mobility and broadband absorption make it promising for ultrafast photodetection. However, its low optical absorption limits responsivity, while the absence of a bandgap results in high dark current, constraining the signal-to-noise ratio and efficiency. Although silicon (Si) photodetectors normally offer fabrication compatibility, their performance is severely hindered by interface trap states and optical shading. To overcome these limitations, we demonstrate an epitaxial graphene/n-Si heterojunction photodiode. This device utilizes graphene epitaxially grown on germanium integrated with a transferred Si thin film, eliminating polymer residues and interface defects common in transferred graphene. As a result, the fabricated photodetector achieves an ultralow dark current of 1.2 × 10−9 A, a high responsivity of 1430 A/W, and self-powered operation at room temperature. This work provides a strategy for high-sensitivity and low-power photodetection and demonstrates the practical integration potential of graphene/Si heterostructures for advanced optoelectronics.

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