Broadband photoresponse of graphene photodetector from visible to long-wavelength infrared wavelengths

Shinpei Ogawa ,Masaaki Shimatani ,Shoichiro Fukushima ,Tetsuya Ono ,Yasushi Kanai ,Satoshi Okuda ,Kazuhiko Matsumoto

doi:10.1117/1.oe.58.5.057106

Abstract

Graphene-based transistors were investigated as simple photodetectors for a broad range of wavelengths. Graphene transistors were prepared using p-doped silicon (Si) substrates with a SiO2 layer, and source and drain electrodes. Monolayer graphene was fabricated by chemical vapor deposition and transferred onto the substrates, and the graphene channel region was then formed. The photoresponse was measured in the broadband wavelength range from the visible, near-infrared (NIR), and mid- to long-wavelength IR (MWIR to LWIR) regions. The photoresponse was enhanced by the photogating induced by the Si substrate at visible wavelengths. Enhancement by the thermal effect of the insulator layer became dominant in the LWIR region, which indicates that the photoresponse of graphene-based transistors can be controlled by the surrounding materials, depending on the operation wavelength. These results are expected to contribute to provide the key mechanism of high-performance graphene-based photodetectors.

Highlights

Graphene is a single atomic layer of carbon with a hexagonal lattice, which results in a unique bandgap structure as Dirac cones.[1]
The photoresponse was measured in the visible, NIR, middle wavelength IR (MWIR), and long-wavelength IR (LWIR) regions
The Vbg and Vsd dependence of Iph and the gate current were measured to investigate this phenomenon. These results provided direct evidence of the photogating effect induced by the depletion layer between the Si substrate and the SiO2 layer at visible wavelengths at room temperature (RT), which correspond to the Si bandgap

Summary

Introduction

Graphene is a single atomic layer of carbon with a hexagonal lattice, which results in a unique bandgap structure as Dirac cones.[1] Such structures produce exciting optoelectronic properties, such as fast electron mobility and broadband absorption that ranges from at least the ultraviolet region to the terahertz region.[2] Many applications are expected for these structures, such as transistors,[3] photodetectors,[4] biological sensors,[5] and supercapacitors.[6] Other two-dimensional materials have been applied to photodetectors.[7,8] In particular, black phosphorus[9,10] has been widely studied for infrared (IR) detector applications due to its bandgap in the middle wavelength IR (MWIR) region. The main disadvantage of graphene is lack of bandgap, which leads to high dark current. This can be overcome by using graphene nanoribbons.[11,12] we have investigated graphene as an advanced material with an aim to realize photodetectors based on a new concept.

Results

Discussion

Conclusion